416C, 426C, 428C, 436C & 438C BACKHOE LOADERS TRANSMISSION Caterpillar


Systems Operation

Usage:

Introduction

When the words "use again" are in the description, the specification given can be used to determine if a part can be used again. If the part is equal to or within the specification given, use the part again.

When the word "permissible" is in the description, the specification given is the "maximum or minimum" tolerance permitted before adjustment, repair and/or new parts are needed.

A comparison can be made between the measurements of a worn part and the specifications of a new part to find the amount of wear. A part that is worn can be used again if an estimate of the remainder of its service life is good. If a short service life is expected, replace the part.


Components Of The Power Train
(1) Flywheel. (2) Engine. (3) Torque converter. (4) Transmission.

Power from diesel engine (2) is sent from flywheel (1) to torque converter (3) through a conventional flex drive plate arrangement.

A pilot bore in the flywheel provides alignment for the front end of the torque converter during installation.

Torque converter (3) features a free wheel clutch that allows the converter stator to free wheel during high speed, low load conditions, such as roading the machine. A freewheeling stator changes the converter into a fluid coupling for better efficiency at the high speed end.

Transmission (4) features a manual four-speed, direct-drive helical gear, constant mesh, synchronized arrangement, coupled with hydraulically shifted forward and reverse shuttle clutches.

Torque Converter

The torque converter hydraulically connects the engine to the transmission. There is no direct mechanical connection between the engine and the transmission.

When the machine works against a load, the torque converter can multiply the torque from the engine and send a higher torque to the transmission. The oil for the operation of torque converter (1) comes from the transmission oil pump. Oil is directed to the transmission circuit and to the torque converter circuit. The torque converter inlet oil pressure is controlled by relief valve (2). The relief valve limits the pressure to torque converter (1) to 750 kPa (110 psi). Outlet oil from the converter flows through transmission oil cooler and into the lubrication and cooling system.


(1) Torque converter. (2) Inlet relief valve (torque converter).


Torque Converter
(3) Flex plate. (4) Housing. (5) Turbine. (6) Impeller. (7) Stator. (8) Stator clutch.

The torque converter has four main parts: housing (4), impeller [pump] (6), turbine (5) and stator (7). The housing is connected to the engine flywheel through flex plate (3). Impeller (6) and housing (4) are connected and turn with the engine flywheel at engine speed. Turbine (5) turns the transmission input shaft (not shown). Stator (7) is installed stationary on stator support (not shown). Impeller (6), which turns with housing (4) at engine speed, directs the oil toward the outside of the impeller and against the blades of turbine (5). The force of the oil hitting the blades of the turbine, causes turbine (5) and transmission input shaft to rotate. The rotation of the transmission input shaft provides power to the transmission.

Oil returns through the stator vanes to the impeller. The stator vanes direct the oil back to the impeller, causing a torque increase. When the speed of turbine (5) is the same as the speed of impeller (6), stator clutch (8) permits the stator to turn freely with engine rotation for more efficient operation.

When turbine torque is greater than impeller torque the stator is locked in place. Torque is multiplied only when the stator is held in place.

Transmission

Two-Wheel Drive


Transmission
(1) Input shaft assembly. (2) Forward input gear. (3) Reverse idler input gear. (4) Forward clutch pack. (5) Forward clutch piston. (6) Reverse idler shaft. (7) Reverse clutch piston. (8) Reverse clutch pack. (9) Reverse idler driven gear. (10) Reverse input gear. (11) Caged roller bearing assembly. (12) First speed gear. (13) First and second speed synchronizer assembly. (14) Second speed gear. (15) Third speed gear. (16) Third and fourth speed synchronizer assembly. (17) Fourth speed gear. (18) Output shaft. (19) Forward driven gear. (20) Countershaft. (21) Implement pump drive shaft.

The transmission features a manual four-speed, direct-drive helical gear, constant mesh, synchronized arrangement, coupled with hydraulically shifted forward and reverse shuttle clutches.

The shuttle is a multi-disc clutch arrangement with two clutch packs contained within the input shaft assembly. Each clutch pack contains six plates and six discs. The clutches are engaged hydraulically and released by spring force.

To make the vehicle move, the clutch engagement is done through an electrical harness connected to the electro-hydraulic solenoid control valve, forward/reverse selector valve. This hydraulically engages forward clutch (4) or reverse clutch (8).

Input shaft assembly (1) sends the power from the torque converter turbine to the forward/reverse shuttle clutches. The input shaft assembly rotates the same direction as the flywheel. Therefore, the plates also rotate the same direction at the same speed as the input shaft.

The input shaft assembly provides four internal oil passages. Two internal oil passages are for lubrication and cooling of the shuttle. The remaining two internal oil passages are for the engagement of the forward clutch pack or the reverse clutch pack.

Forward input gear (2) and reverse input gear (10) are free to rotate on input shaft assembly (1) when neither clutch pack, forward or reverse, is not engaged. The discs rotate with the input gears.

Reverse idler shaft (6) and gears (3) and (9) provide reverse rotation to countershaft (20) when the reverse clutch is engaged. Reverse idler driven gear (9) is engaged with reverse input gear (10). The power flows from the reverse idler driven gear (9) to reverse idler input gear (3) when reverse clutch pack (8) is engaged.

Countershaft (20) transfers power to the speed range gears on output shaft (18) either from forward input gear (2) or from reverse idler input gear (3), depending on which clutch pack is engaged.

Output shaft (18) carries speed range gears (12), (14), (15), and (17) and synchronizer assemblies (13) and (16). All but one of the speed range gears rotate on fluted areas, which are for lubrication purposes. First speed gear (12) is supported by two caged roller bearing assemblies (11).


Synchronizer Assembly (Shown in NEUTRAL)
(21) Cup. (22) Shifter fork. (23) Sliding collar. (24) Cone. (25) Split pin. (26) Blocker pin.

The synchronizer assembly consists of two inner synchronizer cones (24). The cones are mounted to sliding collar (23) by a series of alternating alignment blocker pins (26) and spring loaded split pins (25). The inner diameter of sliding collar (23) is splined to output shaft (18). The speed range gears have matching splines. Synchronizer cups (21) are splined to the speed range gears, thus rotate with the speed range gears.

When shifter fork (22) moves sliding collar (23) to engage a speed gear, the sliding collar comes in contact with the shoulder on the blocker pins (26). The force exerted on the blocker pins causes the blocker pin to push the cone against the cup. Now the sliding collar (23) assembly and output shaft (18) are rotating at the same speed as the speed gear, thus synchronization has occurred.

If there is a torsional load or mismatch of speeds between the speed range gear and the output shaft, the shoulder of the blocker pin will prevent the sliding collar from engaging. When the speeds are synchronized and there is no torsional or side load on the blocker pin, the sliding collar will continue to slide as the shifter fork moves it.

The spring loaded split pins (25) will collapse and act as a locking mechanism to keep the sliding collar (23) and output shaft (18) engaged.

The four speed shift lever is on the floor. To shift speed range gears, the operator neutralizes the transmission solenoid control valve, by depressing the neutralizer button on the shift lever and holding it. Activating the neutralizer button releases a directional clutch, forward or reverse, and thus putting the transmission in NEUTRAL. Now, the operator can select any speed range gear, even while the vehicle is moving. Once the shift is complete, the neutralizer button must be deactivated (released). The speed shift is completed and the directional clutch is engaged again. Power is now being sent from the output shaft to the rear axle.

Only one synchronizer assembly can be engaged at a time.

Power Flows

First Or Second Speed Forward


Power Flow In First Speed Forward
(1) Input shaft assembly. (2) Forward input gear. (3) Reverse idler input gear. (4) Forward clutch pack. (5) Forward clutch piston. (6) Reverse idler shaft. (7) Reverse clutch piston. (8) Reverse clutch pack. (9) Reverse idler driven gear. (10) Reverse input gear. (11) Caged roller bearing assembly. (12) First speed gear. (13) First and second speed synchronizer assembly. (14) Second speed gear. (15) Third speed gear. (16) Third and fourth speed synchronizer assembly. (17) Fourth speed gear. (18) Output shaft. (19) Driven gear. (20) Countershaft. (21) Implement pump drive shaft.


Synchronizer Assembly (Shown in NEUTRAL)
(21) Cup. (22) Shifter fork. (23) Sliding collar. (24) Cone. (25) Split pin. (26) Blocker pin.

The torque converter turbine drives input shaft assembly (1). To engage the forward clutch, the operator moves the direction control lever, mounted on the steering wheel column, to the forward position. This causes oil pressure to be sent through input shaft assembly (1) to pressurize forward clutch piston (5). Forward clutch pack (4) is engaged and sends the power to forward input gear (2).

Forward input gear (2) transmits the power to driven gear (19), which turns countershaft (20), which is constantly engaged with the speed range gears. For first speed gear (12) or second speed gear (14) to be engaged with output shaft (18), the neutralizer button, located on the shift lever, must be activated to neutralize the transmission solenoid control valve. Activating the neutralizer button releases the directional clutch, forward, thus putting the transmission in NEUTRAL. Now the shift lever can be moved to first or second gear. Shifter fork (22) slides synchronizer collar (23) to the right so first speed gear (12) engages with output shaft (18), or to the left so second speed gear (14) engages with output shaft (18).

If the speed of the speed gear and the output shaft are the same and there is no torsional loads, synchronizer assembly (13) will engage the speed gear with the output shaft. Once the shift is complete the neutralizer button must be deactivated (released). The speed shift is completed and the directional clutch is engaged again. Power is now being sent from the output shaft to the rear axle.

Third Or Fourth Speed Forward


(1) Input shaft assembly. (2) Forward input gear. (3) Reverse idler input gear. (4) Forward clutch pack. (5) Forward clutch piston. (6) Reverse idler shaft. (7) Reverse clutch piston. (8) Reverse clutch pack. (9) Reverse idler driven gear. (10) Reverse input gear. (11) Caged roller bearing assembly. (12) First speed gear. (13) First and second speed synchronizer assembly. (14) Second speed gear. (15) Third speed gear. (16) Third and fourth speed synchronizer assembly. (17) Fourth speed gear. (18) Output shaft. (19) Driven gear. (20) Countershaft. (21) Implement pump drive shaft.


Synchronizer Assembly (Shown in NEUTRAL)
(21) Cup. (22) Shifter fork. (23) Sliding collar. (24) Cone. (25) Split pin. (26) Blocker pin.

The torque converter turbine drives input shaft assembly (1). To engage the forward clutch, the operator moves the direction control lever, mounted on the steering wheel column, to the forward position. This causes oil pressure to be sent through input shaft assembly (1) to pressurize forward clutch piston (5). Forward clutch pack (4) is engaged and sends the power to forward input gear (2).

Forward input gear (2) transmits the power to driven gear (19), which turns countershaft (20), which is constantly engaged with the speed range gears. For third speed gear (15) or fourth speed gear (17) to be engaged with output shaft (18), the neutralizer button, located on the shift lever, must be activated to neutralize the transmission solenoid control valve. Activating the neutralizer button releases the directional clutch, forward, thus putting the transmission in NEUTRAL. Now the shift lever can be moved to first or second gear. Shifter fork (22) slides synchronizer collar (23) to the right so third speed gear (15) engages with output shaft (18), or to the left so fourth speed gear (17) engages with output shaft (18).

If the speed of the speed gear and the output shaft are the same and there is no torsional loads, synchronizer assembly (16) will engage the speed gear with the output shaft. Once the shift is complete the neutralizer button must be deactivated (released). The speed shift is completed and the directional clutch is engaged again. Power is now being sent from the output shaft to the rear axle.

First Or Second Speed Reverse


(1) Input shaft assembly. (2) Forward input gear. (3) Reverse idler input gear. (4) Forward clutch pack. (5) Forward clutch piston. (6) Reverse idler shaft. (7) Reverse clutch piston. (8) Reverse clutch pack. (9) Reverse idler driven gear. (10) Reverse input gear. (11) Caged roller bearing assembly. (12) First speed gear. (13) First and second speed synchronizer assembly. (14) Second speed gear. (15) Third speed gear. (16) Third and fourth speed synchronizer assembly. (17) Fourth speed gear. (18) Output shaft. (19) Driven gear. (20) Countershaft. (21) Implement pump drive shaft.


Synchronizer Assembly (Shown in NEUTRAL)
(21) Cup. (22) Shifter fork. (23) Sliding collar. (24) Cone. (25) Split pin. (26) Blocker pin.

The torque converter turbine drives input shaft assembly (1). To engage the reverse clutch, the operator moves the direction control lever, mounted on the steering wheel column, to the reverse position. This causes oil pressure to be sent through input shaft assembly (1) to pressurize reverse clutch piston (7). Reverse clutch pack (8) is engaged and sends power to reverse input gear (10).

Reverse input gear (10) transmits the power to reverse idler driven gear (9), which turns reverse idler shaft (6) and reverse idler input gear (3). Reverse idler input gear (3) transmits the power to driven gear (19), which turns countershaft (20), which is constantly engaged with the speed range gears. The countershaft will rotate in the opposite direction as it would in forward, which gives the reverse direction.

The countershaft is in constant mesh with speed range gears mounted on output shaft (18). For first speed gear (12) or second speed gear (14) to be engaged with output shaft (18), the neutralizer button, located on the shift lever, must be activated to neutralize the transmission solenoid control valve. Activating the neutralizer button releases the directional clutch, reverse, thus putting the transmission in NEUTRAL. Now the shift lever can be moved to first or second gear. Shifter fork (22) slides synchronizer collar (23) to the right so first speed gear (12) engages with output shaft (18), or to the left so second speed gear (14) engages with output shaft (18).

If the speed of the speed gear and the output shaft are the same and there is no torsional loads, synchronizer assembly (13) will engage the speed gear with the output shaft. Once the shift is complete the neutralizer button must be deactivated (released). The speed shift is completed and the directional clutch is engaged. Power is now being sent from the output shaft to the rear axle.

Third Or Fourth Speed Reverse


(1) Input shaft assembly. (2) Forward input gear. (3) Reverse idler input gear. (4) Forward clutch pack. (5) Forward clutch piston. (6) Reverse idler shaft. (7) Reverse clutch piston. (8) Reverse clutch pack. (9) Reverse idler driven gear. (10) Reverse input gear. (11) Caged roller bearing assembly. (12) First speed gear. (13) First and second speed synchronizer assembly. (14) Second speed gear. (15) Third speed gear. (16) Third and fourth speed synchronizer assembly. (17) Fourth speed gear. (18) Output shaft. (19) Forward driven gear. (20) Countershaft. (21) Implement pump drive shaft.


Synchronizer Assembly (Shown in NEUTRAL)
(21) Cup. (22) Shifter fork. (23) Sliding collar. (24) Cone. (25) Split pin. (26) Blocker pin.

The torque converter turbine drives input shaft assembly (1). To engage the reverse clutch, the operator moves the direction control lever, mounted on the steering wheel column, to the reverse position. This causes oil pressure to be sent through input shaft assembly (1) to pressurize reverse clutch piston (7). Reverse clutch pack (8) is engaged and sends power to reverse input gear (10).

Reverse input gear (10) transmits the power to reverse idler driven gear (9), which turns reverse idler shaft (6) and reverse idler input gear (3). Reverse idler input gear (3) transmits the power to driven gear (19), which turns countershaft (20), which is constantly engaged with the speed range gears. The countershaft will rotate in the opposite direction as it would in forward, which gives the reverse direction.

The countershaft is in constant mesh with speed range gears mounted on output shaft (18). For third speed gear (15) or fourth speed gear (17) to be engaged with output shaft (18), the neutralizer button, located on the shift lever, must be activated to neutralize the transmission solenoid control valve. Activating the neutralizer button releases the directional clutch, reverse, thus, putting the transmission in NEUTRAL. Now the shift lever can be moved to first or second gear. Shifter fork (22) slides synchronizer collar (23) to the right so third speed gear (14) engages with output shaft (18), or to the left so fourth speed gear (17) engages with output shaft (18).

If the speed of the speed gear and the output shaft are the same and there is no torsional loads, synchronizer assembly (16) will engage the speed gear with the output shaft. Once the shift is complete the neutralizer button must be deactivated (released). The speed shift is completed and the directional clutch is engaged again. Power is now being sent from the output shaft to the rear axle.

Transmission

All-Wheel Drive


Transmission
(1) Input shaft assembly. (2) Forward input gear. (3) Reverse idler input gear. (4) Forward clutch pack. (5) Forward clutch piston. (6) Reverse idler shaft. (7) Reverse clutch piston. (8) Reverse clutch pack. (9) Reverse idler driven gear. (10) Reverse input gear. (11) Countershaft. (12) Front wheel drive input gear (All wheel drive only). (13) Caged roller bearing assembly. (14) First speed gear. (15) Front wheel driven gear. (16) Front wheel drive clutch pack. (17) Front wheel drive clutch piston. (18) Front wheel drive output shaft. (19) First and second speed synchronizer assembly. (20) Second speed gear. (21) Third speed gear. (22) Third and fourth speed synchronizer assembly. (23) Fourth speed gear. (24) Output shaft. (25) Forward driven gear. (26) Implement pump drive shaft.

The transmission features a manual four-speed, direct-drive helical gear, constant mesh, synchronized arrangement, coupled with hydraulically shifted forward and reverse shuttle clutches.

The shuttle is a multi-disc clutch arrangement with two clutch packs contained within the input shaft assembly. Each clutch pack contains six plates and six discs. The clutches are engaged hydraulically and released by spring force.

To make the vehicle move, the clutch engagement is done through a mechanical linkage connected to the electro-hydraulic solenoid control valve, forward/reverse selector valve. This hydraulically engages forward clutch (4) or reverse clutch (8).

Input shaft assembly (1) sends the power from the torque converter turbine to the forward/reverse shuttle clutches. The input shaft assembly rotates the same direction as the flywheel. Therefore, the plates also rotate the same direction at the same speed as the inout shaft.

The input shaft assembly provides three internal oil passages. One internal oil passage is for lubrication and cooling of the shuttle. The remaining two internal oil passages are for the engagement of the forward clutch pack or the reverse clutch pack.

Forward input gear (2) and reverse input gear (10) are free to rotate on input shaft assembly (1) when neither clutch pack, forward or reverse, is not engaged. The discs rotate with the input gears.

Reverse idler shaft (6) and speed range gears (3) and (9) provide reverse rotation to countershaft (11) when the reverse clutch is engaged. Reverse idler driven gear (9) is engaged with reverse input gear (10). The power flows from the reverse idler driven gear (9) to reverse idler input gear (3) when reverse clutch pack (8) is engaged.

Countershaft (11) transfers power to the speed range gears on output shaft (24) either from forward input gear (2) or from reverse idler input gear (3), depending on which clutch pack is engaged.

Output shaft (23) carries speed range gears (14), (20), (21), and (23) and synchronizer assemblies (19) and (22). All but one of the speed range gears rotate on fluted areas, which are for lubrication purposes. First speed gear (14) is supported by two caged roller bearing assemblies (13).


Synchronizer Assembly (Shown in NEUTRAL)
(26) Cup. (27) Shifter fork. (28) Sliding collar. (29) Cone. (30) Split pin. (31) Blocker pin.

The synchronizer assembly consists of two inner synchronizer cones (29). The cones are mounted to sliding collar (28) by a series of alternating alignment blocker pins (31) and spring loaded split pins (30). The inner diameter of sliding collar (28) is splined to output shaft (24). The speed range gears have matching splines. Synchronizer cups (26) are splined to the speed range gears, thus rotate with the speed range gears.

When shifter fork (27) moves sliding collar (28) to engage a speed gear, the sliding collar comes in contact with the shoulder on the blocker pins (31). The force exerted on the blocker pins causes the blocker pin to push the cone against the cup. Now the sliding collar (28) assembly and output shaft (24) are rotating at the same speed as the speed gear, thus synchronization has occurred.

If there is a torsional load or mismatch of speeds between the speed range gear and the output shaft, the shoulder of the blocker pin will prevent the sliding collar from engaging. When the speeds are synchronized and there is no torsional or side load on the blocker pin, the sliding collar will continue to slide as the shifter fork moves it.

The spring loaded split pins (30) will collapse and act as a locking mechanism to keep the sliding collar (28) and output shaft (24) engaged.

The four speed shift lever is on the floor. To shift speed range gears, the operator neutralizes the transmission solenoid control valve, by depressing the neutralizer button on the shift lever and holding it. Activating the neutralizer button releases a directional clutch, forward or reverse, and thus putting the transmission in NEUTRAL. Now, the operator can select any speed range gear, even while the vehicle is moving. Once the shift is complete, the neutralizer button must be deactivated (released). The speed shift is completed and the directional clutch is engaged again. Power is now being sent from the output shaft to the rear axle.

Only one synchronizer assembly can be engaged at a time.

All-Wheel Drive


(32) All-wheel drive switch.

The all-wheel drive attachment will improve mobility and overall loader performance in poor traction conditions.

Power Flows


Transmission
(1) Input shaft assembly. (2) Forward input gear. (3) Reverse idler input gear. (4) Forward clutch pack. (5) Forward clutch piston. (6) Reverse idler shaft. (7) Reverse clutch piston. (8) Reverse clutch pack. (9) Reverse idler driven gear. (10) Reverse input gear. (11) Countershaft. (12) Front wheel drive input gear (All wheel drive only). (13) Caged roller bearing assembly. (14) First speed gear. (15) Front wheel driven gear. (16) Front wheel drive clutch pack. (17) Front wheel drive clutch piston. (18) Front wheel drive output shaft. (19) First and second speed synchronizer assembly. (20) Second speed gear. (21) Third speed gear. (22) Third and fourth speed synchronizer assembly. (23) Fourth speed gear. (24) Output shaft. (25) Forward driven gear. (26) Implement pump drive shaft.

The front drive axle may by engaged at any time by activating the all-wheel drive switch located on the left side of the front dash panel. This switch may be activated when the vehicle is stopped or while it is moving. Parts required with the all-wheel drive attachment are: front wheel driven gear (15), front wheel drive clutch pack (16), and front wheel drive output shaft (18). The front wheel drive output shaft connects the transmission with the steerable front drive axle.

When the operator activates the all-wheel drive switch on the front dash panel, the all-wheel drive solenoid is energized. A passage is opened that allows oil under pressure to flow to front wheel drive output shaft (18). The oil flows through front wheel drive output shaft (18) to engage front wheel drive clutch pack (16). With the front wheel drive clutch pack engaged, input from front wheel drive input gear (12) is transmitted to front wheel driven gear (15). Power from front wheel driven gear (15) is then transmitted through front wheel drive clutch pack (16), and front wheel drive output shaft (18) to an output drive flange connected to the front axle drive shaft.

Transmission Hydraulic System

Two-Wheel Drive


Transmission Hydraulic System in Neutral (Engine Running)
(1) Oil filter with bypass. (2) System relief valve. (3) Transmission solenoid (forward/reverse) control valve. (4) Torque converter. (5) Inlet relief valve for torque converter. (6) Oil cooler. (7) Transmission lubrication system. (8) Oil (sump) reservoir. (9) Suction screen. (10) Oil pump [gerotor]. (11) Relief valve [cold start]. (A) Pressure tap for pump. (B) Reverse clutch pack. (C) Pressure tap for reverse clutch. (D) Pressure tap for forward clutch. (E) Forward clutch pack. (F) Pressure tap for torque converter inlet. (G) Pressure tap for torque converter outlet. (H) Pressure tap for lubrication and cooling. (AA) Activated components in system. (BB) Tank oil. (CC) Converter inlet oil. (DD) Pump oil. (EE) Return oil from converter outlet. (FF) Lubrication oil.

The basic components of the hydraulic system for operation of the transmission and torque converter are: oil reservoir (8), oil suction screen (9), oil pump (10), oil filter (1), torque converter (4), system relief valve (2), solenoid (forward/reverse) control valve (3), relief valve (5) for torque converter inlet, oil cooler (6), the forward clutch pack and the reverse clutch pack.

All oil passages are inside the transmission case and transmission solenoid control valve (3), except the two transmission oil lines connected to oil cooler (6).

Torque Converter, Transmission Pump, Screen And Filter

The oil for the operation, cooling and lubrication of the transmission and torque converter is made available by an internal crescent pump. The pump is located at the transmission input shaft. The torque converter stator support and pump are assembled together and the assembly is bolted to the transmission case. The pump is driven by the torque converter impeller housing.

The oil reservoir for the transmission and torque converter is in the bottom (sump) of the transmission case. Oil from the reservoir first flows through a screen and then through a transmission case passage to the suction side of the positive displacement pump. The oil from the pump flows to the filter and then the transmission hydraulic controls. If there is a restriction in the oil filter or if the viscosity of the oil is very high, such as during a cold start up of the machine, a relief valve (cold start) opens diverting the oil flow directly back to the sump of the transmission.


Location Of Oil Filter

If the pressure differential of the inlet oil pressure to the oil filter is 138 ± 14 kPa (20 ± 2 psi), higher than the outlet oil pressure, the oil filter bypass valve will open.

When the oil does not flow through the oil filter element, unfiltered oil could cause damage to other components in the transmission oil system.

Correct maintenance must be used to make sure that the element does not become plugged and stop the flow of clean oil to the transmission oil system. The filter is mounted to the left side of the transmission case.

The screen is mounted inside the transmission case. The screen can be removed on the right side of case.


Location Of Screen

Power Train Oil Cooler

The transmission oil cooler is mounted on the front of the radiator.


(1) Transmission oil cooler. (A) Oil flow to cooler from transmission. (B) Air flow over cooler. (C) Oil flow from cooler to transmission.

Transmission system oil with high temperature flows out the torque converter outlet to the transmission oil cooler. As oil is flowing through the core assembly, air is flowing around the core assembly. In this way, heat is removed from the oil.

After the oil flows through the cores of the transmission oil cooler, it flows through the outlet passage of the core assembly having a lower temperature. The cooler oil returns to the transmission providing lubrication and cooling.

Transmission Lubrication System


Transmission Lubrication

The only pressure lubrication in the transmission is for the forward and reverse shuttles, discs, plates and bearings. After the oil has been cooled by the oil cooler, the oil will flow through an internal passage on the right side of the transmission case and flow to the right end of the input shaft. The cooled oil flows through the oil passages in the input shaft assembly providing the cooling and lubrication for the bearings, plates and discs.

The other gears and bearings are splash lubricated. The movement of the gears in the oil reservoir causes oil to be thrown on all components.

All-Wheel Drive


Transmission Hydraulic System In Neutral (Engine Running)
(1) Oil filter with bypass. (2) System relief valve. (3) Transmission solenoid (forward/reverse) control valve. (4) Torque converter. (5) Inlet relief valve for torque converter. (6) Oil cooler. (7) Transmission lubrication system. (8) Oil (sump) reservoir. (9) Suction screen. (10) Oil pump [gerotor]. (11) Relief valve [cold start]. (12) All-wheel drive solenoid. (A) Pressure tap for pump. (B) Reverse clutch pack. (C) Pressure tap for reverse clutch. (D) Pressure tap for forward clutch. (E) Forward clutch pack. (F) Pressure tap for torque convert r inlet. (G) Pressure tap for torque converter outlet. (H) Pressure tap for lubrication and cooling. (J) All-wheel drive clutch pack. (K) Pressure tap for All-wheel drive clutch pack. (AA) Activated components in system. (BB) Tank oil. (CC) Converter inlet oil. (DD) Pump oil. (EE) Return oil from converter outlet. (FF) Lubrication oil.

The basic components of the hydraulic system for operation of the transmission and torque converter are: oil filter (1), system relief valve (2), solenoid (forward/reverse) control valve (3), torque converter (4), relief valve (5) for torque converter inlet, oil cooler (6), oil reservoir (8), oil suction screen (9), oil pump (10), all-wheel drive solenoid control valve, and the forward clutch pack and the reverse clutch pack.

All oil passages are inside the transmission case and transmission solenoid control valve (3), except the two transmission oil lines connected to oil cooler (6). An external tube provides oil passage from the all-wheel drive solenoid to the all-wheel drive clutch pack.

Torque Converter, Transmission Pump, Screen And Filter

The oil for the operation, cooling and lubrication of the transmission and torque converter is made available by an internal crescent pump. The pump is located at the transmission input shaft. The torque converter stator support and pump are assembled together and the assembly is bolted to the transmission case. The pump is driven by the torque converter impeller housing.

The oil reservoir for the transmission and torque converter is in the bottom (sump) of the transmission case. Oil from the reservoir first flows through a screen and then through a transmission case passage to the suction side of the positive displacement pump. The oil from the pump flows to the filter and then the transmission hydraulic controls. If there is a restriction in the oil filter or if the viscosity of the oil is very high, such as during a cold start up of the machine, a relief valve (cold start) opens diverting the oil flow directly back to the sump of the transmission.


Location Of Oil Filter

If the pressure differential of the inlet oil pressure to the oil filter is 138 ± 14 kPa (20 ± 2 psi) higher than outlet oil pressure, the oil filter bypass valve will open.

When the oil does not flow through the filter element, unfiltered oil could cause damage to other components in the transmission oil system.

Correct maintenance must be used to make sure that the element does not become plugged and stop the flow of clean oil to the transmission oil system. The filter is mounted to the left side of the transmission case.

The screen is mounted inside the transmission case. The screen can be removed on the right side of case.


Location Of Screen

Power Train Oil Cooler

The transmission oil cooler is mounted on the front of the radiator.


(1) Transmission oil cooler. (A) Oil flow to cooler from transmission. (B) Air flow over cooler. (C) Oil flow from cooler to transmission.

Transmission system oil with high temperature flows out the torque converter outlet to the transmission oil cooler. As oil is flowing through the core assembly, air is flowing around the core assembly. In this way, heat is removed from the oil.

After the oil flows through the cores of the transmission oil cooler, it flows through the outlet passage of the core assembly having a lower temperature. The cooler oil returns to the transmission providing lubrication and cooling.

Transmission Lubrication System


Transmission Lubrication

The only pressure lubrication in the transmission is for the forward and reverse shuttles, discs, plates and bearings. After the oil has been cooled by the oil cooler, the oil will flow through an internal passage on the right side of the transmission case and flow to the right end of the input shaft. The cooled oil flows through the oil passages in the input shaft assembly providing the cooling and lubrication for the bearings, plates and discs.

The other gears and bearings are splash lubricated. The movement of the gears in the oil reservoir causes oil to be thrown on all components.

Hydraulic Controls


Location Of Transmission Solenoid Control Valve.

The transmission solenoid control valve is installed on top of the transmission housing. The transmission solenoid control valve controls the forward, reverse, and neutral functions of the transmission.

This is accomplished by the solenoid control valve directing pressurized oil either to the forward or reverse clutch packs. In the centered or neutral position, clutch pressure is dumped back to the transmission case. The reverse solenoid of the transmission solenoid control valve is electrically connected to the backup alarm switch which activates the back alarm.

The transmission solenoid control valve is also a neutralizing solenoid. Neutralizing the transmission solenoid control is completed by depressing the transmission neutralizer switch located on the gear shift lever or on the loader control lever.


(1) Neutralizer button on gear shift lever. (2) Neutralizer button on loader control lever. (3) All-wheel steer switch on loader control lever.

When either of the neutralizer switches is engaged, the respective solenoid, forward or reverse, is deactivated. Deactivating the transmission control solenoid valve blocks the oil flow from the transmission pump. In the centered or neutral position, clutch pressure is dumped back to the transmission case, thus disengaging the transmission. Activating the respective solenoid, forward or reverse, returns the transmission to its former gear position.

If the transmission solenoid control valve is left in a forward or reverse position when the vehicle is turned off, the transmission solenoid control valve will deactivate the neutral/start switch so the vehicle cannot be started until the transmission solenoid control valve selector valve is returned to the NEUTRAL position at next start-up.


Location Of Direction Control Lever

The forward/reverse solenoids within the transmission solenoid control valve are electrically actuated with the direction control lever mounted on the steering wheel column.

When the transmission solenoid control valve is de-energized the centering springs center the spool blocking the oil flow from the transmission pump. With oil flow blocked to the transmission, the oil pressure in the directional clutch circuit decreases and the directional clutch disengages. When the transmission solenoid is re-energized the oil passage to the transmission is reopened, permitting the refilling of the directional clutches and allowing the transmission to gain pressure again.

Operation

Two-Wheel Drive

Starting The Engine (Transmission in Neutral)


Transmission Hydraulic System In Neutral (Engine Running)
(1) Oil filter with bypass. (2) System relief valve. (3) Transmission solenoid (forward/reverse) control valve. (4) Torque converter. (5) Inlet relief valve for torque converter. (6) Oil cooler. (7) Transmission lubrication system. (8) Oil (sump) reservoir. (9) Suction screen. (10) Oil pump [gerotor]. (11) Relief valve [cold start]. (A) Pressure tap for pump. (B) Reverse clutch pack. (C) Pressure tap for reverse clutch. (D) Pressure tap for forward clutch. (E) Forward clutch pack. (F) Pressure tap for torque converter inlet. (G) Pressure tap for torque converter outlet. (H) Pressure tap for lubrication and cooling. (AA) Activated components in system. (BB) Tank oil. (CC) Converter inlet oil. (DD) Pump oil. (EE) Return oil from converter outlet. (FF) Lubrication oil.

When the engine is started oil pump (10) pulls oil from reservoir (8) through suction screen (9) to the pump. The pump sends the oil through filter (1) to transmission solenoid control valve (3).

With the direction control lever in the NEUTRAL position, oil flow is blocked by the transmission control solenoid valve, thus neither forward or reverse clutch pack can be pressurized. The clutch oil passages are open to drain.

This allows oil not needed by the clutch circuit to flow through the system relief valve to the torque converter circuit onto the lubrication system and finally back to the sump.

Engine Running (Neutral To Forward)


Transmission Hydraulic System
(1) Oil filter with bypass. (2) System relief valve. (3) Transmission solenoid (forward/reverse) control valve. (4) Torque converter. (5) Inlet relief valve for torque converter. (6) Oil cooler. (7) Transmission lubrication system. (8) Oil (sump) reservoir. (9) Suction screen. (10) Oil pump [gerotor]. (11) Relief valve [cold start]. (A) Pressure tap for pump. (B) Reverse clutch pack. (C) Pressure tap for reverse clutch. (D) Pressure tap for forward clutch. (E) Forward clutch pack. (F) Pressure tap for torque converter inlet. (G) Pressure tap for torque converter outlet. (H) Pressure tap for lubrication and cooling. (AA) Activated components in system. (BB) Tank oil. (CC) Converter inlet oil. (DD) Pump oil. (EE) Return oil from converter outlet. (FF) Lubrication oil.

When the direction control lever on the steering wheel column is moved to the forward position (away from the driver), the forward solenoid of the transmission control solenoid valve (3) is electrically activated. The electrical activation of forward solenoid overrides the centering spring allowing the spool to move, thus opening a oil passage for pressurized oil to flow to the forward directional clutch (E).

With the engine running, oil pump (10) pulls oil from reservoir (8), through suction screen (9), to the pump. The oil pump sends the oil through filter (1) and to the transmission control solenoid valve.

An orifice within transmission control solenoid valve establishes a constant flow and pressure of oil to the directional clutches. This allows oil not needed by the transmission circuit to flow to the torque converter circuit.

With the forward position selected, oil is directed to the forward clutch pack. The reverse clutch oil passage is open to drain. Oil fills the forward clutch.

When the directional clutch pack obtains maximum system pressure, relief valve (2) opens, thus helping maintain maximum system pressure to the directional clutch pack.

When relief valve (2) is closed, a bypass orifice within the relief valve still permits the flow of oil to the torque converter at low idle for lubrication and cooling purposes.

Torque converter inlet relief valve (5) controls maximum pressure to the torque converter to prevent damage during cold starts. Normal torque converter pressure is maintained in the torque converter by the restrictions created by the oil cooler and the oil lines leaving the torque converter.

Engine Running (Forward To Reverse)


Transmission Hydraulic System
(1) Oil filter with bypass. (2) System relief valve. (3) Transmission solenoid (forward/reverse) control valve. (4) Torque converter. (5) Inlet relief valve for torque converter. (6) Oil cooler. (7) Transmission lubrication system. (8) Oil (sump) reservoir. (9) Suction screen. (10) Oil pump [gerotor]. (11) Relief valve [cold start]. (A) Pressure tap for pump. (B) Reverse clutch pack. (C) Pressure tap for reverse clutch. (D) Pressure tap for forward clutch. (E) Forward clutch pack. (F) Pressure tap for torque converter inlet. (G) Pressure tap for torque converter outlet. (H) Pressure tap for lubrication and cooling. (AA) Activated components in system. (BB) Tank oil. (CC) Converter inlet oil. (DD) Pump oil. (EE) Return oil from converter outlet. (FF) Lubrication oil.

When the direction control lever on the steering wheel column is moved to the reverse position (toward the driver), the reverse solenoid of the transmission control solenoid valve (3) is electrically activated. The electrical activation of reverse solenoid overrides the centering spring allowing the spool to move, thus opening a oil passage for pressurized oil to flow to the reverse directional clutch (B).

With the engine running, oil pump (10) pulls oil from reservoir (8), through suction screen (9), to the pump. The oil pump sends the oil through filter (1) and to transmission control solenoid valve (3).

An orifice within transmission control solenoid valve establishes a constant flow and pressure of oil to the directional clutches. This allows oil not needed by the transmission circuit to flow to the torque converter circuit.

With the reverse position selected, oil is directed to the reverse clutch pack. The forward clutch oil passage is open to drain. Oil fills the reverse clutch.

When the directional clutch pack obtains maximum system pressure, relief valve (2) opens, thus helping maintain maximum system pressure to the directional clutch pack.

When relief valve (2) is closed, a bypass orifice within the relief valve still permits the flow of oil to the torque converter at low idle for lubrication and cooling purposes.

Torque converter inlet relief valve (5) controls maximum pressure to the torque converter to prevent damage during cold starts. Normal torque converter pressure is maintained in the torque converter by the restrictions created by the oil cooler and the oil lines leaving the torque converter.

All-Wheel Drive

The all-wheel drive attachment will improve mobility and overall loader performance in poor traction conditions.


(1) All-wheel drive switch.

The front drive axle may be engaged at any time by activating the all-wheel drive switch (1) on the left side of the front console. This switch may be activated when the vehicle is stopped or while it is moving. The basic components required with the all-wheel drive attachment are, the all-wheel drive switch, the all-wheel drive solenoid valve, the all-wheel drive transmission, the all-wheel drive clutch pack on the all-wheel drive output shaft, a steerable front drive axle, and a front drive shaft with a guard. The front drive shaft connects the all-wheel drive output shaft with the steerable front drive axle.

Starting The Engine (Transmission in Neutral) All-Wheel Drive Off


Transmission Hydraulic System In Neutral (Engine Running)
(1) Oil filter with bypass. (2) System relief valve. (3) Transmission solenoid (forward/reverse) control valve. (4) Torque converter. (5) Inlet relief valve for torque converter. (6) Oil cooler. (7) Transmission lubrication system. (8) Oil (sump) reservoir. (9) Suction screen. (10) Oil pump [gerotor]. (11) Relief valve [cold start]. (12) All-wheel drive solenoid. (A) Pressure tap for pump. (B) Reverse clutch pack. (C) Pressure tap for reverse clutch. (D) Pressure tap for forward clutch. (E) Forward clutch pack. (F) Pressure tap for torque converter inlet. (G) Pressure tap for torque converter outlet. (H) Pressure tap for lubrication and cooling. (J) All-wheel drive clutch pack. (K) Pressure tap for All-wheel drive clutch pack. (AA) Activated components in system. (BB) Tank oil. (CC) Converter inlet oil. (DD) Pump oil. (EE) Return oil from converter outlet. (FF) Lubrication oil.

When the engine is started oil pump (10) pulls oil from reservoir (8) through suction screen (9) to the pump. The pump sends the oil through filter (1) to transmission solenoid control valve (3).

With the direction control lever in the NEUTRAL position, oil flow is blocked by the transmission control solenoid valve, thus neither forward or reverse clutch pack can be pressurized. The clutch oil passages are open to drain.

This allows oil not needed by the transmission circuit to flow to the torque converter circuit through the system relief valve.

With the all-wheel drive switch in the OFF position, oil flow to the all-wheel drive clutch pack (J) is blocked by the all-wheel drive solenoid valve (12) and the all-wheel drive clutch pack is connected to drain.

Engine Running (Forward) All-Wheel Drive Activated


Transmission Hydraulic System
(1) Oil filter with bypass. (2) System relief valve. (3) Transmission solenoid (forward/reverse) control valve. (4) Torque converter. (5) Inlet relief valve for torque converter. (6) Oil cooler. (7) Transmission lubrication system. (8) Oil (sump) reservoir. (9) Suction screen. (10) Oil pump [gerotor]. (11) Relief valve [cold start]. (12) All-wheel drive solenoid. (A) Pressure tap for pump. (B) Reverse clutch pack. (C) Pressure tap for reverse clutch. (D) Pressure tap for forward clutch. (E) Forward clutch pack. (F) Pressure tap for torque converter inlet. (G) Pressure tap for torque converter outlet. (H) Pressure tap for lubrication and cooling. (J) All-wheel drive clutch pack. (K) Pressure tap for All-wheel drive clutch pack. (AA) Activated components in system. (BB) Tank oil. (CC) Converter inlet oil. (DD) Pump oil. (EE) Return oil from converter outlet. (FF) Lubrication oil.

When the direction control lever on the steering wheel column is moved to the forward position (away from the driver), the forward solenoid of the transmission control solenoid valve (3) is electrically activated. The electrical activation of forward solenoid overrides the centering spring allowing the spool to move, thus opening a oil passage for pressurized oil to flow to the forward directional clutch (E).

With the engine running, oil pump (10) pulls oil from reservoir (8), through suction screen (9), to the pump. The oil pump sends the oil through filter (1) and to the transmission control solenoid valve.

An orifice within transmission control solenoid valve establishes a constant flow and pressure of oil to the directional clutches. This allows oil not needed by the transmission circuit to flow to the torque converter circuit.

With the forward position selected, oil is directed to the forward clutch pack. The reverse clutch oil passage is open to drain. Oil fills the forward clutch.

When the directional clutch pack obtains maximum system pressure, relief valve (2) opens, thus helping maintain maximum system pressure to the directional clutch pack.

When relief valve (2) is closed, a bypass orifice within the relief valve still permits the flow of oil to the torque converter at LOW idle for lubrication and cooling purposes.

Torque converter inlet relief valve (5) controls maximum pressure to the torque converter to prevent damage during cold starts. Normal torque converter pressure is maintained in the torque converter by the restrictions created by the oil cooler and the oil lines leaving the torque converter.

With the all-wheel drive switch in the ON position, oil flows through a smaller internal passage to the all-wheel solenoid valve. With the all-wheel drive solenoid energized, a passage opens to an external tube that provides an oil passage to all-wheel drive clutch pack (J).

Engine Running (Forward To Reverse) All-Wheel Drive Activated


Transmission Hydraulic System
(1) Oil filter with bypass. (2) System relief valve. (3) Transmission solenoid (forward/reverse) control valve. (4) Torque converter. (5) Inlet relief valve for torque converter. (6) Oil cooler. (7) Transmission lubrication system. (8) Oil (sump) reservoir. (9) Suction screen. (10) Oil pump [gerotor]. (11) Relief valve [cold start]. (12) All-wheel drive solenoid. (A) Pressure tap for pump. (B) Reverse clutch pack. (C) Pressure tap for reverse clutch. (D) Pressure tap for forward clutch. (E) Forward clutch pack. (F) Pressure tap for torque converter inlet. (G) Pressure tap for torque converter outlet. (H) Pressure tap for lubrication and cooling. (J) All-wheel drive clutch pack. (K) Pressure tap for All-wheel drive clutch pack. (AA) Activated components in system. (BB) Tank oil. (CC) Converter inlet oil. (DD) Pump oil. (EE) Return oil from converter outlet. (FF) Lubrication oil.

When the direction control lever on the steering wheel column is moved to the reverse position (toward the driver), the reverse solenoid of the transmission control solenoid valve (3) is electrically activated. The electrical activation of reverse solenoid overrides the centering spring allowing the spool to move, thus opening a oil passage for pressurized oil to flow to the reverse directional clutch (B).

With the engine running, oil pump (10) pulls oil from reservoir (8), through suction screen (9), to the pump. The oil pump sends the oil through filter (1) and to transmission control solenoid valve (3).

An orifice within transmission control solenoid valve establishes a constant flow and pressure of oil to the directional clutches. This allows oil not needed by the transmission circuit to flow to the torque converter circuit.

With the reverse position selected, oil is directed to the reverse clutch pack. The forward clutch oil passage is open to drain. Oil fills the reverse clutch.

When the directional clutch pack obtains maximum system pressure, relief valve (2) opens, thus helping maintain maximum system pressure to the directional clutch pack.

When relief valve (2) is closed, a bypass orifice within the relief valve still permits the flow of oil to the torque converter at LOW idle for lubrication and cooling purposes.

Torque converter inlet relief valve (5) controls maximum pressure to the torque converter to prevent damage during cold starts. Normal torque converter pressure is maintained in the torque converter by the restrictions created by the oil cooler and the oil lines leaving the torque converter.

With the all-wheel drive switch in the ON position, oil flows through a smaller internal passage to the all-wheel solenoid valve. With the all-wheel drive solenoid energized, a passage opens to an external tube that provides an oil passage to all-wheel drive clutch pack (J).

Caterpillar Information System:

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416C, 426C, 428C, 436C & 438C BACKHOE LOADERS TRANSMISSION Introduction
3054 ENGINE SUPPLEMENT FOR 416C, 426C, 428C, 436C & 438C BAC Water Separator
3054 ENGINE SUPPLEMENT FOR 416C, 426C, 428C, 436C & 438C BAC Water Separator
3054 ENGINE SUPPLEMENT FOR 416C, 426C, 428C, 436C & 438C BAC Engine & Transmission
3054 ENGINE SUPPLEMENT FOR 416C, 426C, 428C, 436C & 438C BAC Engine, Torque Converter, Transmission & Implement Pump
3054 ENGINE SUPPLEMENT FOR 416C, 426C, 428C, 436C & 438C BAC Cab
3054 ENGINE SUPPLEMENT FOR 416C, 426C, 428C, 436C & 438C BAC Oil Filter & Oil Filter Base
3054 ENGINE SUPPLEMENT FOR 416C, 426C, 428C, 436C & 438C BAC Fuel Filter
3054 ENGINE SUPPLEMENT FOR 416C, 426C, 428C, 436C & 438C BAC Turbocharger
3054 ENGINE SUPPLEMENT FOR 416C, 426C, 428C, 436C & 438C BAC Radiator, Oil Cooler & Condenser
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416C, 426C, 428C, 436C, & 438C BACKHOE LOADERS POWER TRAIN Introduction
416C, 426C, 428C, 436C, & 438C BACKHOE LOADERS POWER TRAIN Tires & Wheels (Rear)
416C, 426C, 428C, 436C, & 438C BACKHOE LOADERS POWER TRAIN Axle Group (Rear)
416C, 426C, 428C, 436C, & 438C BACKHOE LOADERS POWER TRAIN Differential (Rear)
416C, 426C, 428C, 436C, & 438C BACKHOE LOADERS POWER TRAIN Pinion Assembly (Rear)
416C, 426C, 428C, 436C, & 438C BACKHOE LOADERS POWER TRAIN Wheel Stud
416C, 426C, 428C, 436C, & 438C BACKHOE LOADERS POWER TRAIN Final Drive Planetary Carrier Hub
416C, 426C, 428C, 436C, & 438C BACKHOE LOADERS POWER TRAIN Axle Housing (Front) (All Wheel Drive)
416C, 426C, 428C, 436C, & 438C BACKHOE LOADERS POWER TRAIN Final Drive And Axle Housing (Rear) (All Wheel Steer)
416C, 426C, 428C, 436C, & 438C BACKHOE LOADERS POWER TRAIN Brakes (Rear) (All Wheel Steer)
416C, 426C, 428C, 436C, & 438C BACKHOE LOADERS POWER TRAIN Differential (Rear) (All Wheel Steer)
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