Systems Operation

Usage:

General Information

SMCS Code: 3000; 3100; 4000

Location of the Power Train Components
(1) Output transfer gears. (2) Transmission. (3) Transmission planetary. (4) Upper drive shaft. (5) Torque converter updrive transfer gears. (6) Torque converter. (7) Engine. (8) Front final drives. (9) Front differential. (10) Front drive shaft. (11) Center bearing. (12) Center drive shaft. (13) Rear drive shaft. (14) Rear differential. (15) Rear final drives.

Power from diesel engine (7) is sent from the flywheel to torque converter (6). Power from the output shaft of the torque converter is sent to torque converter updrive transfer gears (5).

Power from the updrive transfer gears is sent through upper drive shaft (4) to the input shaft of transmission (2).

Six hydraulically activated clutches in the transmission, give four forward speeds and four reverse speeds. Speed and direction selections are made based on switch inputs selected by the operator.

The transmission output shaft is connected to output transfer gears (1) by splines. Power is sent from the output transfer gears through rear drive shaft (13) to rear differential (14). The output transfer gears also sends power to front differential (9) through center drive shaft (12), center bearing (11) and front drive shaft (10).

The pinions, bevel gears and gears of each differential turn their respective axles. The axles are connected to final drives (8) and (15). The final drives turn the wheels.

Torque Converter

SMCS Code: 3101; 3102; 3129; 3130; 3131; 3134; 3135; 3136

Torque Converter Components
(1) Rotating housing. (2) Impeller. (3) Gear. (4) Turbine. (5) Inlet port. (6) Spider assembly. (7) Carrier. (8) Output shaft. (9) Hub. (10) Hub. (11) Stator. (12) Carrier assembly. (13) Outlet port.

The torque converter sends power from the engine to the torque converter updrive transfer gears and on to the planetary transmission. The torque converter uses oil from the transmission pump to multiply the torque to the transmission. When the machine works against a low load, the torque multiplication is low. When the machine works against a high load, the torque multiplication is higher. A higher torque can then be sent to the transmission during high load conditions. During no load conditions, the torque converter does not multiply torque from the engine.

The converter housing is bolted to the flywheel housing. Spider assembly (6), rotating housing (1), hub (10), impeller (2) and oil pump drive gear (3) are driven by the engine flywheel and rotate as a unit.

Flow of Power in the Torque Converter
(1) Rotating housing. (2) Impeller. (3) Gear. (4) Turbine. (5) Inlet port. (6) Spider assembly. (7) Carrier. (8) Output shaft. (9) Hub. (10) Hub. (11) Stator. (12) Carrier assembly. (13) Outlet port.

Oil for the operation of the torque converter goes through inlet passage (5) in carrier (7) to impeller (2). The rotation of the impeller gives force to the oil. The impeller sends the oil toward the outside of the impeller, around the inside of housing (1) to turbine (4). The force of the oil hitting the blades of the turbine causes the turbine to turn. At this point in time, the torque given to the turbine by the force of the oil from the impeller can not be more than the torque output of the engine to the impeller.

As the oil goes from the turbine, it moves in a direction opposite to the direction of impeller (2) rotation. Stator (11) causes the oil to change direction. Since the stator is connected to carrier assembly (12) and can not turn, most of the oil is sent back to the impeller. The remainder of the oil goes from the stator through outlet passage (13) to the converter outlet relief valve.

The force of the oil from the stator can now add to the torque output from the engine to the impeller. This extra force can give an increase to the torque output of the engine to the turbine. The larger the difference between the speeds of the impeller and the turbine, the larger the amount of force of the oil from the stator. It is the load on the machine that changes the speed of the turbine. The higher the load, the larger the difference in the speeds of the impeller and the turbine. It is the different loads on the machine that control the amount of torque multiplication that the force of the oil from the stator can add.

Torque Converter Updrive Transfer Gears

SMCS Code: 3101; 3105; 3108; 3159

Torque Converter Updrive Assembly
(1) Torque converter updrive housing. (2) Output drive section. (3) Steering, brake and pilot pump group and axle oil cooling pump group drive section. (4) Transmission charging pump group drive section.

Torque converter updrive housing (1) is fastened to the engine flywheel housing. The updrive has two functions:

1. To transfer drive from the engine and torque converter to the upper drive shaft to raise the drive shaft height over the rear differential assembly.

2. To drive the implement pump, the steering, brake and pilot pump, the transmission charging pump, the torque converter scavenge pump and the axle oil cooling pump (if equipped).

Section A-A
(1) Torque converter updrive housing. (2) Output yoke. (5) Gear. (6) Shaft. (7) Torque converter. (8) Drive gear. (9) Pump drive gear. (10) Torque converter output shaft.

Torque converter (7) is connected to the engine flywheel by splines. The drive output from the engine goes through the torque converter to output shaft (10). Shaft (10) is connected to drive gear (8) by splines. Gear (8) drives gear (5). Gear (5) is connected to shaft (6) by splines. Output yoke (2) is connected to shaft (6) by splines. Yoke (2) is connected to the upper drive shaft that drives the transmission input shaft.

Power flow from the torque converter is through output shaft (10), drive gears (8) and (5) to output shaft (6) and yoke (2).

Section B-B
(1) Torque converter updrive housing. (3) Steering, brake and pilot pump group and axle oil cooling pump group drive section. (4) Transmission charging pump group drive section. (7) Torque converter. (9) Pump drive gear. (11) Drive gear for implement pump, torque converter scavenge pump, steering, brake and pilot pump and axle oil cooling pump (if equipped). (12) Implement pump group and torque converter scavenge pump group drive section. (13) Idler gear. (14) Drive gear for transmission charging pump.

Torque converter assembly (7) and pump drive gear (9) are bolted together and rotate as a unit at engine speed. Pump drive gear (9) engages gear (14). Gear (14) is connected by splines to the drive shaft of the transmission charging pump group.

Pump drive gear (9) also drives idler gear (13). Idler gear (13) drives gear (11) which is connected by splines to the drive shaft of the implement pump, torque converter scavenge pump, steering, brake and pilot pump and axle oil cooling pump (if equipped).

Oil for lubrication of the updrive transfer gears comes from two sources. The main lubrication supply comes from the transmission oil pump, through the oil filter and into the updrive transfer housing in two places. This oil branches off into internal passages to supply oil to the bearings of the updrive transfer gears and is also directed through orifices on to the meshing teeth of the gears. The other lubrication source is from oil supplied by the transmission hydraulic controls for the operation of the torque converter. This oil is directed through passages in the updrive transfer housing for lubrication of idler gear (13).

The accumulated oil in the bottom of the torque converter updrive housing is picked up by the torque converter scavenge pump and returned to the reservoir in the transmission output transfer gear case.

Torque Converter Hydraulic System

SMCS Code: 3100; 3101

Schematic for the Torque Converter Hydraulic System
(1) Oil filter. (2) Torque converter. (3) Transmission hydraulic controls. (4) Body of relief valve for converter outlet. (5) Relief valve for converter outlet. (6) Oil pump. (7) Screen. (8) Oil reservoir. (9) Oil cooler. (10) Torque converter scavenge pump. (A) Pressure tap for oil pump (on filter). (B) Pressure tap for converter inlet [P3]. (C) Pressure tap for relief valve. (D) Pressure tap for converter outlet. (E) Pressure tap for lubrication.

Two control valves make up the hydraulic system for the torque converter. These valves are the ratio valve for torque converter inlet pressure and the relief valve for torque converter outlet pressure.

Torque Converter Ratio Valve

SMCS Code: 3137

Location of the Torque Converter Ratio Valve
(1) Transmission selector and pressure control valve. (2) Ratio valve for the torque converter. (3) Spring. (4) Slug.

The torque converter ratio valve is part of transmission selector and pressure control valve (1) in the transmission hydraulic control group. The torque converter ratio valve controls the maximum pressure to the converter. The main purpose of the ratio valve is to prevent damage to converter components when the engine is started and the oil is cold. It limits the maximum pressure to the converter to approximately 980 kPa (142 psi). This pressure is not adjustable.

The pressure to the torque converter, caused by restrictions to flow, is felt against the left end of ratio valve (2). This pressure pushes against the whole diameter of the valve spool.

Pressure from the speed clutch oil is felt in the slug chamber of the valve spool. This pressure pushes against only the diameter of slug (4).

The pressure, on the left end of the valve, needed to move the valve to the right, is less than the pressure in the slug chamber and the force of spring (3), needed to move the valve to the left.

When the inlet pressure to the torque converter gets to its maximum, the valve spool moves to the right. This lets extra oil go to the reservoir. When the pressures are again in balance, the valve moves back to the left.

All oil not used by the clutches goes to the ratio valve for the torque converter.

Relief Valve (Torque Converter Outlet)

SMCS Code: 3133-OL

Location of the Torque Converter Outlet Relief Valve

The outlet relief valve is mounted on the torque converter updrive housing. The relief valve for converter outlet controls the maximum pressure of oil inside the torque converter.

Torque Converter Outlet Relief Valve
(1) Spring. (2) Valve spool. (3) Spacers. (4) Poppet valve. (5) Valve body. (6) Spring.

Oil leaving the torque converter enters valve body (5) through the inlet passage. The oil passes through a hole in valve spool (2), unseats poppet valve (4) and acts against the end of the spool.

As the pressure of the converter outlet oil increases, the valve spool moves against the effect of spring (1). As the spool moves, the outlet passage and the inlet passage are connected. Oil from the converter outlet relief valve then flows to the transmission oil cooler.

Spacers (3) are used to adjust the opening pressure of the valve to 415 ± 35 kPa (60 ± 5 psi).

Transmission Hydraulic System

SMCS Code: 3000

Schematic for the Transmission Hydraulic System
(1) Outlet line from torque converter. (2) Torque converter. (3) Updrive transfer gear case. (4) Torque converter outlet relief valve. (5) Inlet line to torque converter. (6) Transmission oil pump. (7) Lubrication line for torque converter updrive transfer gears. (8) Transmission oil filter. (9) Transmission hydraulic controls. (10) Transmission case. (11) Output transfer gear case. (12) Oil cooler. (13) Outlet line (from oil cooler). (14) Torque converter scavenge screen. (15) Torque converter scavenge pump. (16) Return line from updrive transfer gear case. (17) Supply line to oil pump. (18) Magnetic screen.

The transmission hydraulic system has a common reservoir. The reservoir is at the bottom of output transfer gear case (11). It supplies oil for the operation of the torque converter and transmission hydraulic systems. It also supplies lubrication oil to the different components in the system.

Oil is drawn from the reservoir through magnetic screen (18) by transmission oil pump (6). Pump (6) sends pressure oil to transmission oil filter (8).

The oil flows through the filter. If restrictions are present in the oil filter, a bypass valve in the filter housing allows the oil to bypass the filter.

Lubrication line (7) goes from transmission oil filter (8) to updrive transfer gear case (3). When the engine is first started, line (7) lets any air in the suction section of the pump to go out of the pump. This allows operation of the pump to start faster.

After the engine is running, line (7) lets a specific amount of oil go to the torque converter updrive transfer gear case for lubrication of the updrive components.

From filter (8), the oil flows to transmission hydraulic controls (9). The transmission selector and pressure control valve (part of the transmission hydraulic controls), controls the pressure and flow of the oil to the transmission clutches for engagement. It also controls the inlet oil to torque converter (2).

Inlet oil, for operation of the torque converter, flows through line (5). The inlet pressure valve for the torque converter (part of the selector and pressure control valve) controls the oil pressure to the torque converter. Leakage oil from torque converter (2) is also used for lubrication of the torque converter components.

After lubrication of the torque converter components, oil flows to the bottom of updrive transfer gear case (3). Lubrication oil from the updrive transfer gears also flows to the bottom of gear case (3). The oil in the bottom of the case is drawn through screen (14) by scavenge pump (15) and flows through line (16) to the reservoir in output transfer gear case (11).

Outlet oil from the converter flows to torque converter outlet relief valve (4). Relief valve (4) maintains the pressure inside the converter at 415 kPa (60 psi) minimum. From the outlet relief valve, the oil flows through line (1) to oil cooler (12).

After flowing through the cooler, the oil at a lower temperature, flows through outlet line (13) to the transmission planetary. This oil is for lubrication of the transmission.

Transmission Oil Pump

SMCS Code: 3066

Location of the Transmission Oil Pump

Oil Pump Construction
(1) Cover assembly. (2) Body assembly. (3) Manfild assembly. (4) Gear. (5) Gear.

The oil pump is a single-section, gear-type pump mounted on the torque converter updrive housing.

The main components of the oil pump are: body assembly (2), cover assembly (1), manifold assembly (3), gear (4) and gear (5).

Drive gear (5) is connected by splines to the pump drive gear in the torque converter updrive housing.

In operation, oil comes from the reservoir in the output transfer gear case, through the magnetic screen to an opening in manifold assembly (3). The oil goes to the lower part of body (2). The oil fills the spaces between the teeth of gears (4) and (5). As the gears turn, oil is pushed from body (2). The oil goes through another passage in manifold assembly (3) to an oil line. The oil then goes to the filter.

Transmission Oil Filter

SMCS Code: 3004; 3067

Location of the Transmission Oil Filter

The transmission oil filter is located above the torque converter updrive housing in the engine compartment of the machine.

Oil Filter Components
(1) Bypass valve. (2) Spring. (3) Plug. (4) Inlet passage. (5) Outlet passage. (6) Base. (7) Element. (8) Housing. (9) Plug.

Pressure oil, from the oil pump, flows into filter base (6), through inlet passage (4). The oil flows through the filter base to housing (8). Oil fills the space between the inside of housing (8) and filter element (7). Normally, oil flows through the filter element and then to the outlet passage. The oil then flows to the remainder of the transmission hydraulic system. The filter element stops any debris that is in the oil.

If the filter element becomes full of debris, the restriction to the flow of oil causes a pressure increase inside the filter. The increase in pressure causes bypass valve (1) to open. The oil then flows to the transmission hydraulic system. When the oil does not flow through the filter element, it is dirty and can cause damage to other components in the system.

Correct maintenance must be used to make certain that filter element (7) does not become full of debris and stop the flow of clean oil to the transmission hydraulic system.

Transmission Magnetic Screen

SMCS Code: 3030

Location of the Magnetic Tube and Screen (Transmission Not Installed)

A magnetic screen is located inside the output transfer gear case. Oil from the bottom of the output transfer gear case flows through an inlet passage. As the oil flows through the screen, foreign particles that are in the oil are stopped by the screen and can not go into the transmission hydraulic system.

After the oil flows through the screen, it flows around and through magnets. The magnets are installed on the tube assembly so that the same magnetic ends are next to each other. Smaller metal particles that go through the screen are stopped and held by the magnets. These magnets will not allow the metal particles to go with the oil through the transmission hydraulic system.

The oil then flows through the outlet passage to the transmission oil pump.

Transmission Oil Cooler

SMCS Code: 1375

Location of the Transmission Oil Cooler
(1) Oil cooler. (2) Coolant inlet/outlet tube (obscured). (3) Oil inlet port. (4) Oil outlet port.

Coolant from the engine enters cooler (1) through inlet/outlet tube (2). The coolant flows through the many long tubes that are in the cooler. The coolant then returns to the engine cylinder block via the inlet/outlet tube.

Transmission Oil Cooler Schematic
(1) Oil cooler.

Transmission system oil with a high temperature comes from the torque converter outlet relief valve through inlet port (3). The flow of oil is around and along the many tubes inside the cooler. In this process, heat is removed from the oil and is transferred to the coolant of the engine. The engine coolant flows through the tubes inside the cooler and removes the heat from the oil. The coolant is then cooled by the cooling system of the engine.

After the oil flows along the tubes in the cooler, it flows out through outlet port (4) at the bottom and has a lower temperature. The colder oil then flows to the transmission for lubrication and cooling.

Torque Converter Scavenge Pump

SMCS Code: 3115

Location of the Torque Converter Scavenge Pump

The torque converter scavenge pump is a single-section gear-type pump mounted on the back of the hydraulic implement pump.

Oil Pump Construction
(1) Bolts. (2) Body assembly. (3) Cover assembly. (4) Manifold assembly. (5) Gear assembly. (6) Seal. (7) Seal. (8) Bolts. (9) Gear assembly. (10) Seals (two). (11) Bearings (four).

The main components of the oil pump are: body assembly (2), cover assembly (3), manifold assembly (4), gear assembly (5) and gear assembly (9).

Gear assembly (5) is connected by splines to the hydraulic implement pump which is driven by the pump drive section of the torque converter updrive transfer gears.

Leakage oil from the torque converter and lubricating oil for the gears and bearings in the torque converter updrive housing is removed from the base of the torque converter housing by the scavenge pump. The oil is returned to the transmission oil reservoir in the base of the output transfer gear case.

In operation, oil comes from the torque converter updrive housing, through a screen to an opening in manifold assembly (4). The oil goes to the lower part of body assembly (2). The oil fills the spaces between the teeth of gears (5) and (9). As the gears turn, oil is pushed from body assembly (2). The oil goes through another passage in manifold assembly (4) to an oil line. The oil then goes to the output transfer gear case.

Torque Converter Scavenge Screen

Location of the Torque Converter Scavenge Screen

A wire gauze screen located in the suction line at the bottom of the torque converter updrive housing prevents any debris or large metal particles from entering the torque converter scavenge pump.

Transmission

SMCS Code: 3030; 3064; 3155; 3160; 3169; 3190

Transmission Components
(1) Ring gear for No. 1 clutch. (2) Coupling gear. (3) No. 1 clutch. (4) No. 2 sun gear. (5) No. 2 clutch. (6) Ring gear for No. 2 clutch. (7) No. 2 and No. 3 carrier. (8) No. 3 clutch. (9) Ring gear for No. 3 clutch. (10) No. 4 carrier. (11) No. 4 sun gear. (12) No. 4 clutch. (13) Ring gear for No. 4 clutch. (14) No. 5 clutch. (15). Rotating hub. (16) No. 6 clutch. (17) Ring gear for No. 6 clutch. (18) No. 6 planetary gears. (19) No. 6 carrier. (20) No. 1 carrier. (21) No. 1 sun gear. (22) No. 6 sun gear. (23) Output shaft. (24) Input shaft. (25) No. 1 planetary gears. (26) No. 2 planetary gears. (27) No. 3 planetary gears. (28) No. 4 planetary gears. (29) Housing assembly.

The transmission has six hydraulically activated clutches that give four speeds FORWARD and four speeds REVERSE. Speed and direction are selected by the transmission control depending on the shifting request of the operator.

The transmission is fastened to the case for the output transfer gears and is connected to the torque converter updrive by the upper drive shaft. Input power to the transmission comes from the torque converter via the upper drive shaft.

A speed clutch and a direction clutch must both be engaged, in that order, to send power through the transmission. The chart gives the combination of the clutches engaged for each FORWARD and REVERSE speeds.

The two clutches, No. 1 and No. 2, nearest the input end of the transmission are the direction clutches. The No. 1 clutch is the REVERSE direction clutch. The No. 2 clutch is the FORWARD direction clutch.

The No. 3, No. 4, No. 5 and No. 6 clutches are the speed clutches. The No. 3 clutch gives FOURTH speed. The No. 4 clutch gives THIRD speed. The No. 5 clutch gives SECOND speed. The No. 6 clutch gives FIRST speed.

First Speed Forward

Power Flow in First Speed Forward (No. 2 and No. 6 Clutches Engaged)
(4) No. 2 sun gear. (5) No. 2 clutch. (6) Ring gear for No. 2 clutch. (7) No. 2 and No. 3 carrier. (9) Ring gear for No. 3 carrier. (10) No. 4 carrier. (11) No. 4 sun gear. (13) Ring gear for No. 4 clutch. (16) No. 6 clutch. (17) Ring gear for No. 6 clutch. (18) No. 6 planetary gears. (19) No. 6 carrier. (22) No. 6 sun gear. (23) Output shaft. (24) Input shaft. (26) No. 2 planetary gears. (27) No. 3 planetary gears. (28) No. 4 planetary gears. (29) Housing assembly.

When the transmission is in FIRST SPEED FORWARD, No. 6 and No. 2 clutches are engaged. The No. 2 clutch holds ring gear (6) for the No. 2 clutch stationary. The No. 6 clutch holds ring gear (17) for the No. 6 clutch stationary. Input shaft (24) turns No. 2 sun gear (4). No. 2 sun gear turns No. 2 planetary gears (26).

Since ring gear (6) is held stationary by the No. 2 clutch, planetary gears (26) move around the inside of the ring gear. The movement of planetary gears (26) causes No. 2 and No. 3 carrier (7) to turn in the same direction as input shaft (24). As the No. 2 and No. 3 carrier turns, No. 3 planetary gears (27) turn. The No. 3 planetary gears (27) turn. The No. 3 planetary gears turn ring gear (9) for the No. 3 clutch and output shaft (23).

Ring gear (9) turns No. 4 carrier (10). As the No. 4 carrier turns, No. 4 planetary gears (28) turn. The No. 4 planetary gears turn ring gear (13) for the No. 4 clutch, which is fastened to housing assembly (29) by bolts. The No. 4 planetary gears also turn No. 4 sun gear (11). No. 4 sun gear turns output shaft (23). Housing assembly (29) turns sun gear (22) for No. 6 clutch (16).

Since ring gear (17) is held stationary by the No. 6 clutch, planetary gears (18) move around inside of the ring gear. The movement of planetary gears (18) and No. 6 carrier (19), turns output shaft (23).

As a result, torque to output shaft (23), is divided through No. 3 planetary gears (27), No. 4 sun gear (11) and No. 6 sun gear (22). From the output shaft, power goes through the output transfer gears to the differentials.

Second Speed Forward

When the transmission is in SECOND SPEED FORWARD, No. 5 and No. 2 clutches are engaged. The No. 2 clutch holds ring gear (6) for the No. 2 clutch stationary. The No. 5 clutch holds rotating hub (15) stationary. Input shaft (24) turns No. 2 sun gear (4). No. 2 sun gear turns No. 2 planetary gears (26).

The No. 3 planetary gears turn ring gear (9) for the No. 3 clutch and output shaft (23). Ring gear (9) turns No. 4 carrier (10). As the No. 4 carrier turns, No. 4 planetary gears (28) turn. The No. 4 planetary gears turn ring gear (13) for the No. 4 clutch, which is fastened to housing assembly (29) by bolts. The No. 4 planetary gears also turn No. 4 sun gear (11). No. 4 sun gear turns output shaft (23).

Since rotating hub (15) is held stationary by No. 5 clutch (14), power is sent through the No. 5 clutch to rotating hub (15). Rotating hub (15) turns output shaft (23).

As a result, torque to output shaft (23) is divided through No. 3 planetary gears (27), No. 4 sun gear (11) and rotating hub (15). From the output shaft, power goes through the output transfer gears to the differentials.

Third Speed Forward

When the transmission is in THIRD SPEED FORWARD, No. 4 and No. 2 clutches are engaged. The No. 2 clutch holds ring gear (6) for the No. 2 clutch stationary. The No. 4 clutch holds ring gear (13) for the No. 4 clutch stationary. Input shaft (24) turns No. 2 sun gear (4). No. 2 sun gear turns No. 2 planetary gears (26). The No. 3 planetary gears turn ring gear (9) for the No. 3 clutch and output shaft (23). Ring gear (9) turns carrier No. 4 (10).

Since ring gear (13) is held stationary by the No. 4 clutch, planetary gears (28) move around the inside of the ring gear. The movement of planetary gears (28) and No. 4 carrier (10), causes No. 4 sun gear (11) to turn. No. 4 sun gear turns output shaft (23).

As a result, torque to output shaft (23) is divided through No. 3 planetary gears (27) and No. 4 sun gear (11). From the output shaft, power goes through the output transfer gears to the differentials.

Fourth Speed Forward

When the transmission is in FOURTH SPEED FORWARD, No. 2 and No. 3 clutches are engaged. The No. 2 clutch holds ring gear (6) for the No. 2 clutch stationary. The No. 3 clutch holds ring gear (9) for the No. 3 clutch stationary. Input shaft (24) turns No. 2 sun gear (6). No. 2 sun gear turns No. 2 planetary gears (26).

Since ring gear (9) is held stationary by the No. 3 clutch, the movement of No. 2 and No. 3 carrier (7) causes No. 3 planetary gears (27) to move around the inside of the ring gear. The No. 3 planetary gears turn output shaft (23). From the output shaft, power goes through the output transfer gears to the differentials.

First Speed Reverse

Power Flow in First Speed Reverse (No. 1 and No. 6 Clutches Engaged)
(1) Ring gear for No. 1 clutch. (2) Coupling gear. (3) No. 1 clutch. (7) No. 2 and No. 3 carrier. (9) Ring gear for No. 3 clutch. (10) No. 4 carrier. (11) No. 4 sun gear. (13) Ring gear for No. 4 clutch. (16) No. 6 clutch. (17) Ring gear for No. 6 clutch. (18) No. 6 planetary gears. (19) No. 6 carrier. (20) No. 1 carrier. (21) No. 1 sun gear. (22) No. 6 sun gear. (23) Output shaft. (24) Input shaft. (25) No. 1 planetary gears. (27) No. 3 planetary gears. (28) No. 4 planetary gears. (29) Housing assembly.

When the transmission is in FIRST SPEED REVERSE, No. 1 and No. 6 clutches are engaged. The No. 1 clutch holds ring gear (1) for the No. 1 clutch stationary. The No. 6 clutch holds ring gear (17) for the No. 6 clutch stationary. Input shaft (24) turns No. 1 sun gear (21). No. 1 sun gear turns No. 1 planetary gears (25). No. 1 carrier (20) is in direct mechanical connection with ring gear (1).

Since ring gear (1) is held stationary by the No. 1 clutch, so is No. 1 carrier (20). The movement of No. 1 planetary gears (25) causes coupling gear (2) to turn in the opposite direction of input shaft (24). Coupling gear (2) is in direct mechanical connection with No. 2 and No. 3 carrier (7). As the No. 2 and No. 3 carrier turns, No. 3 planetary gears (27) turn.

The No. 4 planetary gears also turn No. 4 sun gear (11). No. 4 sun gear turns output shaft (23). Housing assembly (29) turns sun gear (22) for No. 6 clutch (16).

Since ring gear (17) is held stationary by the No. 6 clutch, planetary gears (18) move around the inside of the ring gear. The movement of planetary gears (18) and No. 6 carrier (19), turns output shaft (23).

As a result, torque to output shaft (23) is divided through No. 3 planetary gears (27), No. 4 sun gear (11) and No. 6 sun gear (22). From the output shaft, power goes through the output transfer gears to the differentials.

Second Speed Reverse

When the transmission is in SECOND SPEED REVERSE, No. 1 and No. 5 clutches are engaged. The No. 1 clutch holds ring gear (1) for the No. 1 clutch stationary. The No. 5 clutch holds rotating hub (15) stationary.

Input shaft (24) turns No. 1 sun gear (21). No. 1 sun gear turns No. 1 planetary gears (25). No. 1 carrier (20) is in direct mechanical connection with ring gear (1).

Since rotating hub (15) is held stationary by No. 5 clutch (14), power is sent through the No. 5 clutch to rotating hub (15). Rotating hub (15) turns output shaft (23).

Third Speed Reverse

When the transmission is in THIRD SPEED REVERSE, No. 1 and No. 4 clutches are engaged. The No. 1 clutch holds ring gear (1) for the No. 1 clutch stationary. The No. 4 clutch holds ring gear (13) for the No. 4 clutch stationary. Input shaft (24) turns No. 1 sun gear (21).

No. 1 sun gear turns No. 1 planetary gears (25). No. 1 carrier (20) is in direct mechanical connection with ring gear (1).

Fourth Speed Reverse

When the transmission is in FOURTH SPEED REVERSE, No. 1 and No. 3 clutches are engaged. The No. 1 clutch holds ring gear (1) for the No. 1 clutch stationary. The No. 3 clutch holds ring gear (9) for the No. 3 clutch stationary. Input shaft (24) turns No. 1 sun gear (21). No. 1 sun gear turns No. 1 planetary gear (25). No. 1 carrier (20) is in direct mechanical connection with ring gear (1).

Transmission Lubrication

SMCS Code: 3030

Planetary Lubrication
(1) Oil supply passage. (2) Oil supply passage.

All planet gears and bearings are pressure lubricated. After the oil has been cooled by the oil cooler, it will enter through oil passages (1) and (2) and an orifice in the transmission end plate.

Oil for lubrication of the No. 1 clutch comes through an orifice in the transmission end plate.

Oil supply passage (1) is for lubrication of clutches No. 2, No. 3, No. 4 and rotating clutch No. 5.

Oil for the No. 6 clutch is supplied through oil supply passage (2).

All clutch leakage oil and return oil flows to the bottom of the transmission case. This oil then flows to the main oil reservoir in the output transfer gear case.

The restrictions to the flow of oil inside the planetary keep the lubrication pressure above 152 kPa (22 psi) at high idle.

Transmission Hydraulic Control

SMCS Code: 3073

The transmission hydraulic control regulates the oil pressure to the torque converter, transmission clutches and lubrication circuits and controls the flow of oil to the clutches.

Transmission Hydraulic Control (Side View)
(1) Solenoids. (2) Solenoid manifold. (3) Top manifold. (4) Selector and pressure control valve. (5) Plate. (6) Selector valve group. (7) Cover.

The transmission hydraulic control is installed on the top of the transmission planetary group. The control consists of solenoids (1), manifold (2), top manifold (3), selector and pressure control valve group (4), plate (5) and selector valve group (6). Speed selector spool for first and third speed is behind cover (7).

Transmission Hydraulic Control (Top View)
(8) No. 3 clutch solenoid. (9) No. 4 clutch solenoid. (10) No. 5 clutch solenoid. (11) P1 pressure tap. (12) P3 pressure tap. (13) Oil tube (inlet from pump). (14) P2 pressure tap. (15) Oil tube (outlet to torque converter). (16) No. 2 clutch solenoid. (17) No. 6 clutch solenoid. (18) No. 1 clutch solenoid. (19) Plug for load piston.

Inlet oil for operation of the hydraulic control comes from the transmission oil filter and flows through tube (13) to the selector and pressure control valve.

Oil for the operation of the torque converter flows through tube (15) and an oil line to the torque converter.

The clutch solenoids direct pump oil to the ends of the selector spools. The selector spools move to send oil to engage a clutch.

Transmission Hydraulic Control (Bottom View)
(6) Selector valve group. (20) Passage to No. 3 clutch. (21) Passage to No. 5 clutch. (22) Passage to No. 2 clutch. (23) Passage to No. 1 clutch. (24) Passage to No. 6 clutch. (25) Passage to No. 4 clutch.

Oil to the clutches is sent through openings (20), (21), (22), (23), (24) and (25) in the selector valve group. The selector valve group is attached to the top of the planetary group.

Selector and Pressure Control Valve (Transmission)

SMCS Code: 3083

Selector and Pressure Control Valve Group and Selector Valve Group
(1) Modulation relief valve. (2) Second and fourth speed selection spool. (3) First and third speed selection spool. (4) Selector control valve group. (5) Converter inlet ratio valve. (6) Direction selection spool. (7) Selector and pressure control valve group. (8) Pressure differential valve. (9) Load piston.

The selector and pressure control valve group and selector valve group are inside the top cover of the transmission.

Selector spools (2), (3) and (6) are moved when oil pressure is applied to one end of the spool. Each solenoid controls oil pressure to the end of one spool. If there is no pressure to the end of a spool, that end is open to drain. The transmission control switches and the electronic transmission control activate the solenoids to control speed and direction of the transmission.

Transmission Hydraulic Control Operation

SMCS Code: 3073

Transmission Hydraulic Controls in the Neutral Position and with the Engine Stopped
(1) No. 2 clutch solenoid. (2) No. 3 clutch solenoid. (3) Oil cooler. (4) Transmission lubrication passage. (5) No. 6 clutch solenoid. (6) No. 1 clutch solenoid. (7) No. 5 clutch solenoid. (8) No. 4 clutch solenoid. (9) Torque converter outlet relief valve. (10) Flow control orifice. (11) Torque converter. (12) Converter inlet ratio valve. (13) Slug. (14) Slug. (15) Modulating relief valve. (16) Direction selection spool. (17) Transmission oil filter. (18) Second and fourth speed selector spool. (19) Oil pump. (20) Pressure differential valve. (21) Load piston. (22) Orifice. (23) First and third speed selector spool. (24) Screen. (25) Reservoir. (A) Pressure tap for lubrication. (B) Pressure tap for converter outlet. (C) Pressure tap for converter inlet [P3]. (D) Pressure tap for speed clutches [P1]. (E) Pressure tap for pump. (F) Pressure tap for direction clutches [P2].

When the engine is started, oil pump (19) pulls oil from reservoir (25) through magnetic screen (24). The pump sends the oil through filter (17) to the selector and pressure control valve group, which is part of the transmission hydraulic controls.

Starting the Engine with the Transmission in the NEUTRAL Position

Transmission Hydraulic Controls in the Neutral Position and with the Engine Running
(2) No. 3 clutch solenoid. (10) Flow control orifice. (12) Converter inlet ratio valve. (15) Modulating relief valve. (18) Second and fourth speed selector spool. (20) Pressure differential valve. (21) Load piston. (AA) Speed clutch oil [P1]. (BB) Direction clutch oil [P2]. (CC) Converter inlet oil [P3]. (DD) Converter outlet oil. (EE) Lubrication oil. (FF) Return oil. (GG) Pilot oil.

When the transmission control is in NEUTRAL, the electronic transmission control activates solenoid (2). The solenoid moves a spool and directs oil to the end of spool (18). Spool (18) moves down and pump oil flows around the spool to No. 3 clutch.

No. 3 clutch is now applied. All of the remaining clutches are open to the reservoir.

Oil, from the pump, flows through flow control orifice (10) to No. 3 clutch, converter inlet ratio valve (12) and pressure differential valve (20).

The oil to pressure differential valve (20) flows through a small orifice in the valve spool and starts to fill the chamber at the top end of the spool. The pressure in the chamber at the top of valve spool (20) increases.

The increase in pressure moves the valve down against the force of the springs. The movement of the valve spool closes a passage from the area behind the bottom end of load piston (21) and the reservoir. At this time, pressure differential valve (20) is in the position shown in the schematic. This allows the pressure in the system to increase.

As the pressure increases in the chamber at the top of pressure differential valve (20), the valve moves down farther. This opens the direction clutch circuit to pump oil. It also closes the bottom end of valve (20) to the reservoir. The pressure in the direction clutch circuit increases. The increase is felt in the spring chamber of valve (20).

When the pressure in the direction clutch circuit is at its maximum, the pressure in the spring chamber, plus the force of the springs, moves valve (20) up. The valve moves up until the flow of pump oil to the direction clutch circuit is stopped. At this time, the movement of the valve spool stops. Now the valve spool moves down and then up (meters), to keep a constant pressure in the direction clutch circuit.

Oil, from the pump, also flows to modulation relief valve (15). It fills the chamber around the modulation relief valve. The oil flows through an orifice in the valve spool and opens the poppet valve at the top of the valve spool. This allows oil to fill the slug chamber at the top of the valve spool.

When the No. 3 clutch is full of oil, the pressure in the speed clutch circuit starts to increase. The increase is felt in the slug chamber at the top of modulation relief valve (15). When the pressure in the speed clutch circuit is at the initial setting of the modulation relief valve, the modulation relief valve moves down. This allows extra oil to flow to the torque converter.

At the same time, pump oil also flows through an orifice to the area between the bottom of load piston (21) and the cover on the selector and pressure control valve body. This area is closed to the reservoir by the position of differential valve (20). The rate of flow to the area behind load piston (21) is restricted by the orifice.

The pressure felt by the modulation relief valve, because of the increase in pressure in the speed clutch circuit, is also felt behind load piston (21). The orifice in the supply passage causes the oil to flow to the area behind the load piston at a specific rate. As the modulation relief valve moves toward the bottom, the load piston moves toward the top. This causes the pressure in No. 3 clutch to increase gradually.

This gradual increase in pressure is known as modulation. The load piston moves more toward the top, against the force of its springs, until the area behind the load piston is open to a drain passage. At this time, modulation stops. As the oil flows out the drain passage, oil continues to fill the area behind the load piston. This keeps the load piston in a position without any further movement.

The operation of the load piston and the modulation relief valve keeps the system pressure at a constant rate.

Pump oil also flows through flow control orifice (10) to converter inlet ratio valve (12). It flows through an orifice in the valve spool and fills the slug chamber. This pressure pushes against only the diameter of the slug.

The oil pressure to the torque converter is felt against the top of valve spool (12). This pressure pushes against the whole diameter of the valve spool.

The pressure on the top of the valve needed to move the valve down is less than the pressure in the slug chamber needed to move the valve up.

When the inlet pressure to the torque converter rises to its maximum, the valve spool moves down. This allows the extra oil to flow to the reservoir. When the pressures are again in balance, the valve moves back up.

All oil, not used by the clutches flows to the torque converter ratio valve.

Shifting from the NEUTRAL Position to the FIRST SPEED FORWARD Position with the Engine Running

Transmission Hydraulic Controls in the First Speed Forward Position and with the Engine Running
(1) No. 2 clutch solenoid. (2) No. 3 clutch solenoid. (5) No. 6 clutch solenoid. (10) Flow control orifice. (12) Converter inlet ratio valve. (14) Slug. (15) Modulating relief valve. (16) Direction selection spool. (18) Second and fourth speed selector spool. (20) Pressure differential valve. (21) Load piston. (23) First and third speed selector spool. (AA) Speed clutch oil [P1]. (BB) Direction clutch oil [P2]. (CC) Converter inlet oil [P3]. (DD) Converter outlet oil. (EE) Lubrication oil. (FF) Return oil. (GG) Pilot oil.

When the transmission control is moved to FIRST SPEED FORWARD, the electronic transmission control activates solenoids (1) and (5) and deactivates solenoid (2). Solenoid (1) moves a spool and directs oil to the top end of direction selection spool (16). Spool (16) moves down and pump oil flows around the spool to No. 2 clutch.

Solenoid (5) moves a spool and directs oil to the left end of speed selection spool (23). Spool (23) moves to the right and pump oil flows around the spool to No. 6 clutch. Solenoid (2) deactivates and directs oil from the top end of speed selection spool (18) to the reservoir. Spool (18) moves up and pump oil is closed to No. 3 clutch.

When the shift to FIRST SPEED FORWARD is made, the No. 3 clutch is opened to the reservoir. The pressure in the system decreases. Springs move modulation relief valve (15) up. Springs move pressure differential valve (20) up until the large orifice at the top end of valve (20) is closed to pump oil by the valve body.

As the pressure differential valve moves up, the chamber behind load piston (21) opens to the reservoir. This allows the springs to move the load piston down.

The speed clutch oil starts to fill No. 6 clutch.

When the No. 6 clutch is full of oil, the pressure in the speed clutch circuit starts to increase. The increase is felt in the slug chamber of modulation relief valve (15) and the chamber at the top of pressure differential valve (20).

The oil to pressure differential valve (20) starts to fill the chamber at the top of the valve spool, through the small orifice.

When the pressure in the No. 6 clutch is approximately 380 kPa (55 psi), pressure differential valve (20) starts to move down. The movement of the valve spool opens No. 2 clutch to pump oil. It also closes a passage from the chamber behind load piston (21) to the reservoir.

When the No. 2 clutch is full of oil, the pressure in the direction clutch circuit increases. The increase is felt in the spring chamber of pressure differential valve (20). The pressure in the spring chamber and the force of the springs moves the valve up against the speed clutch pressure at the top of the valve spool.

As the pressure in the speed clutch circuit increases, the pressure increases in the chamber at the top of pressure differential valve (20).

The increase in pressure moves the valve spool down against the force of the springs. This opens No. 2 clutch to pump oil.

As the pressure in the No. 2 clutch increases, the pressure increases in the spring chamber of valve (20). The increased pressure in the spring chamber and the force of the springs, moves the valve spool up.

This stops the flow of pump oil to the No. 2 clutch. This function continues until the pressure in the No. 2 clutch is at its maximum. At this time, the pressure in the spring chamber and the force of the springs moves the valve spool up, until the flow of oil to the clutch is stopped. Now the valve moves up and down (meters) to keep a constant pressure in the No. 2 clutch. This pressure is approximately 380 kPa (55 psi) less than the pressure in the speed clutch. This difference is determined by the force of the springs of the pressure differential valve.

Oil, from the pump, also flows to modulation relief valve (15). It fills the chamber around the valve spool. The oil flows through an orifice in the valve spool and opens the poppet valve at the top end of the valve spool. This allows oil to fill the slug chamber at the top of the valve spool.

The function of modulation relief valve (15) and load piston (21), is to control the rate of the pressure increase in the speed clutch circuit.

As the pressure in the No. 6 clutch increases, modulation relief valve (15) moves down and load piston (21) moves up. The orifice in the supply passage to the load piston causes the oil to flow to the area behind the load piston at a specific rate. As the modulation relief valve moves down and the load piston moves up, the pressure in No. 6 clutch increases gradually. This gradual increase in pressure is known as modulation.

The load piston moves more toward the top against the force of its springs until the area behind the load piston is open to a drain passage. At this time, modulation stops. As the oil flows out the drain passage, oil continues to fill the area behind the load piston. This keeps the load piston in this position. After the pressures in the clutches are at their maximum, modulation relief valve (15) allows the extra oil to flow to the torque converter.

The operation of the load piston and the modulation relief valve keeps the system pressure at a constant rate.

The oil pressure to the torque converter is felt against the top of valve spool (12). This pressure pushes against the whole diameter of the valve spool.

The pressure on the top of the valve needed to move the valve down is less than the pressure in the slug chamber needed to move the valve up.

All oil, not used by the clutches flows to the torque converter ratio valve.

Transmission Electrical System

SMCS Code: 4800

The main components of the transmission electrical system are the transmission control group, electronic control module, six solenoid valves and transmission neutralizer switch.

Reference: For further information on the transmission electrical system, refer to Electronic Transmission Control System, Systems Operation, Testing and Adjusting and the Electrical Schematic, for the machine that is being serviced.

Electronic Transmission Control (ETC)

Location of the Electronic Transmission Control (ETC)

The electronic transmission control (ETC) for the transmission is located behind the lower panel at the rear of the operator's station. The main function of the ETC is to electronically control the transmission shifts. The ETC receives operator input from the transmission controls and from the autoshift switch to shift the transmission to the desired speed and direction.

Dash Panel
(1) Caterpillar Monitoring System message display.

The Caterpillar Monitoring System message display (1) shows the transmission direction and speed selection.

The ETC also receives input from the transmission neutralizer switch located in the left service brake pedal. This function places the transmission in neutral when the left brake pedal is depressed.

The ETC also controls engine starting and the back-up alarm. The ETC will not allow the engine to be started unless the directional control switch, or lever, is in the neutral position. The back-up alarm is activated any time the directional control switch, or lever, is in the reverse position.

The ETC has built-in system diagnostics to detect faults in the transmission electronic system. The diagnostics are displayed on the Caterpillar Monitoring System message display when the system is placed in the service mode.

Rear Dash Panel
(2) Service connector. (3) Service connector.

The diagnostic service connectors are located on the dash panel at the rear of the operator's compartment. There are two sets of connectors on the dash panel. Service connector (2) is for the connection of a laptop using Electronic Technician (ET) software to diagnose the engine control, the electronic transmission control and various other option controls. Service connector (3) is for the connection of an Elphinstone or Caterpillar Service Box to provide diagnostic access to the Caterpillar Monitoring System and the electronic transmission control.

For Systems Operation, Testing and Adjusting information on the transmission electrical system, make reference to Electronic Transmission Control System, for the machine that is being serviced.

Transmission Controls

Autoshift Switch (STIC Steer Machines)

Rear Dash Panel
(1) Autoshift switch.

Autoshift switch (1) selects manual or automatic transmission shifting. When autoshift switch (1) is turned to the desired gear speed, the transmission will automatically upshift or downshift. The transmission will not automatically upshift to a speed higher than the gear speed selected on autoshift switch (1).

Autoshift Switch (Wheel Steer Machines)

Rear Dash Panel
(2) Auto/Man switch.

Auto/Man switch (2) selects manual or automatic transmission shifting. When the switch is in the automatic position, the transmission will automatically upshift or downshift. The transmission will not automatically upshift to a speed higher than that selected by the operator on the transmission control lever.

STIC Control (STIC Steer Machines)

STIC Control Group
(3) Transmission speed upshift switch. (4) Transmission speed downshift switch. (5) Transmission direction control switch. (6) Steering and transmission lock lever.

The STIC control group is mounted on the operator's station door. Transmission direction control switch (5) is a three position switch that selects neutral, forward or reverse. Transmission speed upshift switch (3) is a momentary contact switch that will select the next higher speed. Transmission speed downshift switch (4) is a momentary contact switch that will select the next lower speed.

Steering and transmission lock lever (6) is used to lock the transmission shift into neutral and is the primary lockout system used to disable the steering.

When lock lever (6) is in the locked position, the STIC control is mechancially locked which disables the steering. A micro switch is also depressed which causes the electronic transmission control (ETC) to shift the transmission to neutral.

When lock lever (6) is moved to the unlocked position, the operator has control of the steering and transmission. The ETC will not shift the transmission into a speed until the direction control switch is first moved to the neutral position.

The steering hydraulic system will also be disabled when the operator's station door is opened. The door must be firmly closed before the STIC control group can be used to steer the machine.

Transmission Control Lever (Wheel Steer Machines)

Transmission Control Lever
(7) Transmission control lever. (8) Transmission neutral lock.

Transmission control lever (7) is used to make transmission direction and speed changes. Moving the lever upwards or downwards selects neutral, forward or reverse. Rotating the grip on the lever selects a transmission speed.

Transmission neutral lock (8) is used to lock transmission control lever (7) in the neutral position.

Parking Brake Interlock

When the parking brake control switch is in the disengaged position, the transmission will shift normally. When the parking brake control switch is in the engaged position, the transmission will not shift out of neutral into first speed forward or first speed reverse.

If the transmission is in first speed forward or first speed reverse when the parking brake is moved to the engaged position, the transmission will be shifted into neutral. If the transmission is in second, third or fourth speed, the transmission will stay engaged.

When the electronic transmission control (ETC) has shifted the transmission into neutral, the ETC will not shift the transmission into a speed until the direction control switch is first moved to the neutral position.

If there is a hydraulic failure and the parking brake cannot be released, a "drive through" feature in first speed is provided. See the Operation and Maintenance Manual, for the machine that is being serviced.

Transmission Neutralizer

Service Brake Pedal
(1) Transmission neutralizer switch. (2) Service brake and transmission neutralizer pedal. (3) Service brake pedal.

The left brake pedal (2) is used to put the transmission in neutral when the service brakes are applied. A micro switch opens when the left brake pedal is partially depressed.

When the brake pedal is released, the micro switch closes and the transmission will engage.

When the transmission is neutralized, the direction clutch solenoid is deactivated. The speed clutch solenoid still remains activated.

Solenoid Valves

Transmission Hydraulic Control Valve
(1) Solenoid valve.

Solenoid valves (1) are installed in the transmission hydraulic controls. The solenoid valves are two position-three way and are normally open to drain. When energized, the solenoid valve spool moves to direct pressure oil to one end of a transmission control valve spool. The transmission control valve spool directs pressure oil to a clutch.

Output Transfer Gears

SMCS Code: 3075

Output Transfer Gears
(1) Case assembly. (2) Drive gear. (3) Bearings. (4) Shims. (5) Shaft. (6) Gear. (7) Yoke assembly. (8) Yoke assembly.

The output transfer gears are at the output side of the transmission. The transmission output shaft is connected to drive gear (2) by splines.

Drive gear (2) is engaged with gear (6). Driven gear (6) is connected to shaft (5) by splines. Yoke assemblies (7) and (8) are connected to shaft (5) by splines. Yoke assembly (7) is connected to the short drive shaft that goes to the rear differential. Yoke assembly (8) is connected to the drive shaft that goes to the bearing cage and then to the front differential.

The flow of power through the output transfer gears is:

a. From the transmission output shaft to drive gear (2).

b. From drive gear (2) to driven gear (6).

c. From driven gear (6) to shaft (5).

At shaft (5) the flow of power divides as follows:

a. Part of the power flows from yoke assembly (7) through a drive shaft to the rear differential.

b. Part of the power goes from yoke assembly (8) through a drive shaft and bearing cage to the front differential.

Shims (4) are used to make an adjustment to the endplay of gear (2).

Output Transfer Gear Lubrication

Since the output transfer gear case is also the reservoir for the transmission circuit, all return oil flows to the bottom of the case. The movement of the gears in the oil causes oil to be thrown on all the components.

Axle Oil Cooling Pump

SMCS Code: 5073

Location of the Axle Oil Cooling Pump
(1) Bypass relief valve for the front axle. (2) Inlet line from the front axle. (3) Bypass relief valve for the rear axle. (4) Inlet line from the rear axle. (5) Outlet line to the front axle oil cooler. (6) Outlet line to the rear axle oil cooler.

Hydraulic Schematic for the Axle Oil Cooling Pump

The axle oil cooling pump assembly is mounted to the rear of the steering, brake and pilot pump on the torque converter updrive housing. Each axle has its own closed system. The section of the pump that is closests to the steering, brake and pilot pump pumps oil to the rear axle housing. The tandem mounted section pumps oil to the front axle housing.

Both pumps circulate the sump oil that is in each axle housing. The oil flows through passages in both the front and the rear axle housings. Each gear pump also causes the oil to flow through an oil cooler. The oil cooler for each alxe is located on the fan side of the radiator. This hydraulic oil circuit helps keep the axle housings and internal brake components cool.

A bypass relief valve is located in each pump. The bypass relief valve limits the amount of oil pressure in the cooling system. The bypass relief valve is rated at 1035 kPa (150 psi).

NOTE: If this pump becomes worn or damaged, replace the pump.

Differential

SMCS Code: 3258

Differential and Bevel Gear Group
(1) Bearing cup and cone. (2) Case. (3) Adjustment ring. (4) Side gear. (5) Carrier. (6) Bolts. (7) Bearing cup and cone. (8) Bearing cup and cone. (9) Lock. (10) Nut. (11) Thrust washer. (12) Pinions. (13) Spider. (14) Bearing. (15) Washer. (16) Ring gear. (17) Case. (18) Adjustment ring. (19) Side gear. (20) Thrust washer. (21) Bearing cup and cone. (22) Shims. (23) Pinion. (24) Housing. (25) Yoke.

A differential divides or causes a balance of the power which is sent to the wheels. When one wheel turns slower than the other, such as when the machine turns, the differential lets the inside wheel go slower in relation to the outside wheel. The differential still sends the same amount of torque to each wheel.

Bevel pinion (23) is connected to yoke (25) by splines. The yoke assembly is connected to a universal joint from the output transfer gears. Pinion (23) is engaged with ring gear (16). Ring gear (16) is fastened to the differential group. Differential carrier (5) is fastened to the axle housing.

The differential group has a case (17). Ring gear (16) is fastened to case (17). Case (17) is fastened to case (2) by bolts (6). Inside the differential group is side gear (4), spider (13), four pinions (12) and side gear (19). Spider (13) is installed between the two cases. When the cases are turned, the spider turns. Pinions (12) are installed on the spider and are engaged with the teeth of side gears (4) and (19). The axle shafts are connected to the side gears by splines. Side gears (4) and (19) turn against thrust washers (11) and (20). Pinions (12) turn on bearings (14).

Nut (10) and lock (9) are used to make an adjustment to the end play (bearing preload) of bearings (7) and (8) for pinion (23).

Shims (22) are used to make an adjustment to the tooth contact (wear pattern) between pinion (23) and ring gear (16).

Rings (3) and (18) are used to make an adjustment to the free movement (backlash) between pinion (23) and ring gear (16). Rings (3) and (18) are also used to make an adjustment to the bearing preload of bearings (1) and (21).

The inside components of the differential get their lubrication from oil thrown around inside the differential. Flat surfaces on spider (13) let oil go to bearings (14). The supply for lubrication oil is a reservoir in the axle housing.

Straight Forward or Straight Reverse Operation

When the machine moves in a straight direction with the same amount of traction under each drive wheel, the same amount of torque on each axle holds the pinions so they do not turn on the spider.

Pinion (23) turns ring gear (16). Ring gear (16) turns cases (2) and (17). Cases (2) and (17) turn spider (13). Spider (13) turns side gears (4) and (19) through pinions (12). Pinions (12) do not turn on the spider. The side gears turn the axle shafts. The same amount of torque is sent to each wheel.

This gives the same effect as if both drive wheels were on one axle shaft.

Operation During a Forward Turn or Operation During a Reverse Turn

When the machine is in a turn, the inside wheel has more resistance to turn than the outside wheel. This resistance causes different torques on the opposite sides of the differential. It is easier for the outside wheel to turn than it is for the inside wheel. The outside wheel starts to turn faster than the inside wheel.

Pinion (23) turns ring gear (16). Ring gear (16) turns cases (2) and (17). Cases (2) and (17) turn spider (13). Spider (13) turns side gears (4) and (19) through pinions (12). Since it takes more force to turn one side gear than it does the other, pinions (12) turn around the spider. As the pinions turn, they move around the side gears. This lets the outside wheel turn faster than the inside wheel.

The same amount of torque is sent to both the inside and outside wheels. This torque is only equal to the amount needed to turn the outside wheel.

Loss of Traction (Wheel Slippage)

When one wheel has more traction than the other, the operation of the differential is the same as in a turn. The same amount of torque is sent to both wheels. This torque is only equal to the amount needed to turn the wheel with the least resistance.

NoSPIN Differential

SMCS Code: 3265

NoSPIN Differential Group
(1) Bevel pinion. (2) Bevel gear. (3) NoSPIN differential and case. (4) Carrier assembly.

The NoSPIN differential is a locking type differential designed to deliver power to both wheels of an axle when ground slip conditions are encountered on one wheel and disengage one side when good traction conditions require overrun, such as the outside wheel in a turn. The NoSPIN differential group is a direct replacement for the standard differential. It is available only in the rear axle group.

When the speeds of the wheels are the same, the NoSPIN differential sends the same amount of torque to each wheel. When the speeds of the wheels are different, the NoSPIN differential sends the torque to the wheel that turns slower. A difference in the speeds of the wheels is caused by a turn.

The NoSPIN differential allows a wheel (axle) to turn faster than the speed of the bevel gear by not engaging it with the bevel gear. For example, during a turn with power, the outside wheel (axle) is not engaged with the bevel gear and turns faster while the inside wheel axle is engaged with the bevel gear and turns at the same speed as the bevel gear. The inside wheel gives the power which moves the machine through the turn.

NoSPIN Differential
(5) Side gear. (6) Driven clutch. (7) Spring. (8) Holdout ring. (9) Holdout ring. (10) Spring. (11) Driven clutch. (12) Side gear. (13) Spring retainer. (14) Spring retainer. (15) Center cam. (16) Snap ring. (17) Spider.

The NoSPIN differential is the same on one side of spider (17) as it is on the other side (symmetrical). The NoSPIN has two springs (7) and (10), two side gears (5) and (12), two driven clutches (6) and (11), two holdout rings (8) and (9), a center cam (15), a snap ring (16) and a spider (17).

The inside splines of side gears (5) and (12) are connected to the sun gears for the final drives by the axle shafts. The outside splines of the side gears are connected to the inside splines of drive clutches (6) and (11). The side gears send the power through the sun gears to the final drives.

Spider (17) is fastened to the differential case and turns at the speed of bevel gear (2). The spider has clutch teeth on both sides. The spider also has one long tooth. The long tooth is spider key (19). Center cam (15) fits inside the spider and is held in position by snap ring (16). The center cam is turned by spider key (19) which fits inside notch (18). Spider key (19) pushes on either side of notch (18). The direction of the machine, forward or reverse, controls which way the spider turns and which side of notch (18) receives the force.

NoSPIN Differential (Left Side Disassembled)
(5) Side gear. (6) Driven clutch. (7) Spring. (8) Holdout ring. (13) Spring retainer. (15) Center cam. (16) Snap ring. (17) Spider.

Springs (7) and (10) fit between the side gears and spring retainers (13) and (14). The outside splines of the spring retainers are connected to the inside splines of the driven clutches. The force of the springs hold the driven clutches against spider (17) and the side gears against the differential case.

Spider and Center Cam
(15) Center cam. (17) Spider. (18) Notch in center cam. (19) Spider key.

Driven clutches (6) and (11) are the same. Each driven clutch has a cam (21) which is part of the clutch. The teeth on the cam engage with the teeth of center cam (15). The teeth of the drive clutches engage with the teeth of spider (17). An annular (in the shape of a circle) groove is between the teeth of the driven clutches and the teeth of the cams.

Clutch and Holdout Ring
(6) Driven clutch. (8) Holdout ring. (20) Notch in holdout ring. (21) Cam.

Holdout rings (8) and (9) are the same. Each holdout ring fits in the annular groove between the teeth of the driven clutches and the teeth of the cams. The teeth of the holdout rings engage with the notches in the center cam. Notch (20) in the holdout ring engages with spider key (19). The spider key controls the movement of the holdout ring in relation to the spider. There is no connection, except friction, between the holdout rings and the driven clutches.

NoSPIN Differential Operation

When a wheel is made to turn faster than the speed of the bevel gear, the "clutch action" (the stopping of power to the drive axle) of the NoSPIN differential will allow this axle to turn faster than the speed of the bevel gear.

The "clutch action" of the NoSPIN differential is as follows: If spider (17) turns, spider key (19) locates center cam (15) and the spider and the center cam turn at the speed of the bevel gear. The center cam turns holdout ring (8) and cam (21) at the speed of the bevel gear. The spider turns driven clutch (6) at the speed of the bevel gear. The driven clutch turns the side gear, axle and wheel at the speed of the bevel gear.

When the wheel is made to turn faster than the speed of the bevel gear, the teeth of the center cam (15) work like ramps and the teeth of cam (21) move up the teeth of the center cam. This action causes driven clutch (6) to become disengaged with the spider. The driven clutch pulls holdout ring (8) out of the grooves in the center cam. The friction between the holdout ring and driven clutch turns the holdout ring until notch (20) in the holdout ring engages with spider key (19). The holdout ring is now turned by the spider key at the speed of the bevel gear. The teeth of the holdout ring are now in a position so they can not engage the notches in the center cam. The driven clutch and cam move around the holdout ring at a speed faster than the speed of the bevel gear. The holdout ring keeps the driven clutch and cam from being engaged with the center cam and spider. The driven clutch, cam, axle shaft and wheel now turn freely.

The opposite side clutch, cam, and holdout ring are held engaged to the center cam and spider by spring (7) as long as the driven wheel turns slower.

When the speed of the wheel that is not engaged becomes slower and near the speed of the bevel gear, the resistance of the ground to the wheel causes the torque on this wheel to be in a small reverse direction. This causes the driven clutch and cam to turn in a direction opposite the direction of the bevel gear. The friction between the holdout ring and the driven clutch causes the holdout ring to move in a direction opposite the direction on the bevel gear.

Notch (20) in the holdout ring moves away from spider key (19). When the teeth of the holdout ring are in a position to engage the notches in center cam (15), the force of the spring causes the driven clutch and cam to move to the inside. The driven clutch pushes the holdout ring. The holdout ring now engages the center cam and is turned at the speed of the bevel gear. The teeth of cam (21) now engage the center cam and the teeth of the drive clutch engage the spider. At this time, both wheels are turned at the same speed.

NOTE: When both wheels are turned at the same speed they do not necessarily have the same torque. For example, when one wheel starts to turn faster on ice (tends to spin), both clutches engage and both wheels turn at the same speed. The wheel that is on ice will have less torque.

Straight Forward Operation

Straight Forward Operation
(5) Side gear. (6) Driven clutch. (11) Driven clutch. (12) Side gear. (17) Spider. (22) Teeth of the spider. (23) Teeth of the driven clutches.

When the machine has straight forward movement, teeth (22) on both sides of spider (17) are fully engaged with teeth (23) of the driven clutches (6) and (11). The teeth of cams (21) are engaged with the teeth of center cam (15). The negative angle of the teeth on the clutches and spider, along with the force of springs (7) and (11), cams (21) and center cam (15), push together and the teeth engage.

In this condition, driven clutches (6) and (11) are fully engaged with spider (17). The driven clutches turn side gears (5) and (12) at the same speed as the bevel gear. The two side gears turn the axle shafts and wheels at the same speed as the bevel gear.

Forward Turn with Power

The travel of the outside wheel, during a turn, is at a longer distance than the travel of the inside wheel. When the machine turns with power, the NoSPIN differential allows the outside wheel to turn faster than the speed of the bevel gear. But it does not allow the inside wheel to turn slower than the speed of the bevel gear. The inside wheel turns at the same speed as the bevel gear.

The teeth of the spider send the drive force to the inside driven clutch. The inside driven clutch turns the inside wheel at the same speed as the bevel gear and provides the power that is needed to move the machine through the turn.

The outside wheel is made to turn (by the traction of the road) at a speed faster than the speed of the bevel gear. This causes the driven clutch for the outside wheel to turn faster than the speed of the bevel gear. The movement of one wheel faster then the other wheel starts the "clutch action" of the NoSPIN differential.

Forward Right Turn with Power
(5) Side gear. (6) Driven clutch. (11) Driven clutch. (12) Side gear. (17) Spider.

The teeth of the cam for the driven clutch for the inside wheel are engaged with the teeth of the center cam (15) and stay in the same position in relation to spider (17). The teeth of the inside drive clutch are engaged with the spider. The teeth on the other side of center cam (15) are used as ramps. The teeth of the cam for the driven clutch for the outside wheel move up the teeth of the center cam.

This causes the outside driven clutch and cam to move away from the spider and center cam. The outside driven clutch and cam are not engaged with the spider and center cam.

The driven clutch for the outside wheel can not be engaged with the spider until the speed of the outside wheel becomes slower and equal to the speed of the bevel gear. The holdout ring keeps the driven clutch and cam from being engaged with the spider and center cam until the machine moves in a straight direction. At this time the operation of the differential is the same as STRAIGHT FORWARD OPERATION.

Forward Turn with No Power

The operation of the NoSPIN differential is the same as for FORWARD TURN WITH POWER. The outside wheel is still made to turn faster (by the traction of the road) than the speed of the bevel gear. The inside wheel is turned at the same speed as the bevel gear.

Straight Reverse Operation

Straight Reverse
(5) Side gear. (6) Driven clutch. (11) Driven clutch. (12) Side gear. (17) Spider. (22) Teeth of the spider. (23) Teeth of the driven clutches.

When the machine moves in a straight reverse direction, teeth (22) on both sides of spider (17) are fully engaged with teeth (23) of driven clutches (6) and (11). Spider (17) turns in the opposite direction than it turns in straight forward. Since the spider turns in an opposite direction, teeth (22) of the spider push against the opposite face of teeth (23) of the driven clutches.

The action of the differential is the same as it is in the STRAIGHT FORWARD DIRECTION.

Reverse Turn with Power

Reverse Right Turn with Power
(5) Side gear. (6) Driven clutch. (11) Driven clutch. (12) Side gear. (17) Spider.

The action of the differential is the same as it is in the FORWARD TURN WITH POWER condition except spider (17) turns in the opposite direction.

Reverse Turn with No Power

The operation of the NoSPIN differential is the same as for REVERSE TURN WITH POWER. The outside wheel is still made to turn faster (by the traction of the road) than the speed of the bevel gear. The inside wheel is turned at the speed as the bevel gear.

Fixed Axle and Oscillating Axle

SMCS Code: 3259; 3260; 3278

The front and rear axle groups incorporate the pinion and bevel gear set, the differential, the disc brakes and the final drives. The front axle group is directly mounted to the machine front frame with a standard differential. The rear axle housing is an oscillating housing with a NoSPIN differential. While the front and rear axle housings and differentials are slightly different, the brake and final drive components and operation are identical.

Power from the transmission output is transferred to the front and rear axle groups by drive shafts from the output transfer gears.

Final Drive

SMCS Code: 4050; 4051

Final Drive Components
(1) Spindle housing. (2) Wheel assembly. (3) Hub. (4) Ring gear. (5) Planetary carrier. (6) Planetary gears. (7) Sun gear. (8) Cover assembly.

Each final drive has the same components. The final drives cause the last speed reduction and torque increase in the power train.

Ring gear (4) is fastened to hub (3). Hub (3) is connected to spindle housing (1) by splines. Spindle housing (1) is fastened to the axle housing. Spindle housing (1), hub (3) and ring gear (4) are held stationary.

The axle shaft is connected to the differential by splines. Sun gear (7) is connected to the axle shaft by splines. Sun gear (7) is engaged with planetary gears (6). Planetary gears (5) are held in planetary carrier (5). Planetary carrier (5) is fastened to wheel assembly (2).

Power from the differential turns the axle shaft. The axle shaft turns sun gear (7). Sun gear (7) turns planetary gears (6). Since ring gear (4) is held by hub (3), the planetary gears move around the inside of ring gear (4). The movement of the planetary gears causes planetary carrier (5) to turn. The planetary carrier is turned in the same direction as sun gear (7) but at a slower speed. The planetary carrier turns wheel assembly (2).

Each final drive has its own oil reservoir. Oil is put into the final drive through a fill plug on outside cover assembly (8). Oil is removed from the final drive through a drain plug on outside cover assembly (8). The components of the final drives are lubricated by the oil inside the final drives.