980G Series II Wheel Loader Power Train Caterpillar

Illustration 1	g00643796
Transmission Hydraulic Control in the NEUTRAL position with the Engine Stopped. (1) Clutch solenoid modulating valve for the Number 2 clutch (2) Clutch solenoid modulating valve for the Number 3 clutch (3) Oil cooler (4) Transmission lubrication passage (5) Clutch solenoid modulating valve for the Number 6 clutch (6) Clutch solenoid modulating valve for the Number 1 clutch (7) Clutch solenoid modulating valve for the Number 5 clutch (8) Clutch solenoid modulating valve for the Number 4 clutch (9) Torque converter outlet relief valve (10) Torque converter housing (11) Flow control orifice (12) Torque converter (13) Converter inlet ratio valve (14) Slug (15) Slug (16) Modulating relief valve (17) Direction selector spool (18) Transmission oil filter (19) Second speed and fourth speed selector spool (20) Oil pump (21) Pressure differential valve (22) Load piston (23) Orifice (24) First speed and third speed selector spool (25) Suction screen and magnet (26) Reservoir (A) Transmission lubrication pressure tap (B) Torque converter outlet pressure tap (C) P3 Torque converter inlet pressure tap (D) P1 Speed clutch pressure tap (E) Pump pressure tap (F) P2 Directional clutch pressure tap

Show/hide table

Personal injury or death can result from sudden machine movement. Sudden movement of the machine can cause injury to persons on or near the machine. To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine.

Show/hide table

Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.

Show/hide table

Escaping fluid under pressure, even a pinhole size leak, can penetrate body tissue, causing serious injury, and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

Operational Checks

Operate the machine in each direction and in all speeds. Note the noises that are not normal and find the sources of the noises. If the machine is not operating correctly, refer to the "Troubleshooting Problem List" below.

Make sure that you check for any service codes that have been generated before troubleshooting a problem.

Reference: For more information on checking for service codes with the Caterpillar Monitoring System, refer to the Service Manual module Testing and Adjusting, "Using Caterpillar Monitoring System to Determine Diagnostic Codes" for the machine that is being serviced.

Reference: For more information on checking for service codes with the Caterpillar Electronic Technician (ET), refer to the Service Manual module Testing and Adjusting, "Using Caterpillar Electronic Technician (ET) to Determine Diagnostic Codes" for the machine that is being serviced.

Troubleshooting Problem List

• There is constant noise in the differential.

• Noise occurs in the differential at different intervals.

• Noise only occurs during turns.

• Lubricant is leaking.

• The drive wheels do not turn but the universal joint turns.

Troubleshooting

Note: In the following section, when components are referenced with a number, refer to the schematic in Illustration 1.

Reference: For additional information about troubleshooting the power train electronic control module (ECM), refer to the Service Manual module Testing and Adjusting, "Troubleshooting Faults with Service Codes" for the machine that is being serviced.

Probable Causes of Power Train Problems

Problem: There is constant noise in the differential.

Probable causes:

1. The level of lubricant is too high or too low.

2. The wrong type of lubricant is being used.

3. Wheel bearings are damaged or improperly adjusted.

4. The ring gear and the pinion do not have correct tooth contact.

5. The ring gear and the pinion are damaged or worn.

6. There is too much backlash between the pinion and the gear or too little backlash between the pinion and the gear.

7. Pinion bearings are loose or worn.

8. Side bearings are loose or worn.

Problem: Noise occurs in the differential at different intervals.

Probable causes:

1. The ring gear does not run evenly because the bolts on the ring gear are not tight or because the ring gear is warped.

2. Differential bearings are loose or broken.

Problem: Noise only occurs during turns.

Probable causes:

1. The differential pinion gears are too tight on the retainer pins or on the pinion shaft.

2. The side gears are too tight in the differential case.

3. Differential pinion gears or side gears are faulty.

4. Thrust washers are damaged or worn.

5. There is too much backlash between the side gears and the pinion gears.

Problem: Lubricant is leaking.

Probable causes:

1. Loss of lubricant through the axle shafts can be caused by any of the following conditions:

   1. The lubricant is above the proper level.

   2. The wrong type of lubricant is being used.

   3. There is a restriction in the axle housing breather.

   4. An oil seal in an axle shaft is worn or installed incorrectly.

2. Loss of lubricant at the pinion shaft can be caused by the following conditions:

   1. The lubricant is above the proper level.

   2. The wrong type of lubricant is being used.

   3. There is a restriction in the axle housing breather.

   4. An oil seal on the pinion shaft is worn or installed incorrectly.

   5. A universal joint flange on the pinion shaft is loose.

Problem: The drive wheels do not turn but the universal joint turns.

Probable causes:

1. An axle shaft is broken.

2. Ring gear teeth are damaged.

3. The side gear or the differential pinion is broken.

4. The differential pinion shaft or the retainer pin is broken.