AD55 Underground Articulated Truck Power Train Caterpillar

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Personal injury or death can result from sudden machine movement. Sudden movement of the machine or the release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury before testing and adjusting the power train system, perform the procedure in the Testing and Adjusting, Troubleshooting, "General Information" section.

Before you troubleshoot a problem, perform the visual checks. Perform the checks with the engine OFF and with the parking brake ENGAGED. Put the transmission control in the NEUTRAL position and put the transmission rotary selector spool in the NEUTRAL position. During the checks, use a magnet to separate ferrous particles from nonferrous particles.

The following checks are the visual checks of the troubleshooting section:

Check: Check the oil level in the transmission

Check the oil level in the transmission. Look for air or for water at the sight gauge. Many problems in the transmission system are caused by low oil levels or by air in the oil. If necessary, add oil to the transmission. In order to determine the correct oil to use, refer to the Operation and Maintenance Manual for the machine that is being serviced.

Problem: The oil level is too high.

Probable Cause:

• The rear seal of the engine crankshaft is allowing engine oil into the torque converter housing.

Problem: There is an indication of water in the oil.

Probable Cause:

Illustration 1	g01081948
Right side view of the Engine (typical example) (1) Power train oil cooler

• Failure of power train oil cooler (1).

Problem: There is an indication of air in the oil.

Probable Cause:

• Perform, "Check: Check for oil leakage".

Problem: The oil level is too low.

Probable Cause:

• Perform, "Check: Check for oil leakage". Add oil before any tests are performed.

Check: Check for oil leakage.

Inspect all the oil lines, the hoses, and the connections for damage or for leaks. Look for oil on the ground under the machine.

Note: If oil can leak out of a fitting or connection, air can enter the system. Air in the system can be as harmful as not enough oil.

Check: Check the transmission oil filter.

Illustration 2	g01081949
Right side of the transmission compartment (2) Transmission oil filters

Remove both transmission oil filters (2). Inspect the filter elements for foreign material.

Note: The transmission oil filter has a bypass valve. The bypass valve allows oil to bypass the oil filter elements whenever the difference in pressure between the inlet oil and the outlet oil in the oil filter is too high. Any oil that does not go through the filter elements goes directly into the power train hydraulic circuit. Dirty oil causes restrictions in the valve orifices, sticking valves, etc.

Problem: Rubber particles are found.

Probable Cause:

• Seal failure.

• Hose failure.

Problem: Shiny steel particles are found.

Probable Cause:

Illustration 3	g01081951
Gear pump (transmission charging and torque converter scavenge) (3) Transmission charging pump section (4) Torque converter scavenge pump section

• Mechanical failure of transmission charging pump section (3).

Check: Check the transmission magnetic screen.

Illustration 4	g01082210
Right side of the transmission case (5) Transmission magnetic screen (behind cover)

Remove transmission magnetic screen (5). Inspect the transmission magnetic screen for foreign material and/or for restrictions.

Problem: Rubber particles are found.

Probable Cause:

• Seal failure.

• Hose failure.

Problem: Bronze or black coarse material is found.

Probable Cause:

• Worn clutches in the transmission.

• Failure of a thrust disc.

Problem: Thin strands that are elastic are found.

Probable Cause:

• Worn clutches in the transmission.

Problem: Iron or steel chips are found.

Probable Cause:

• Broken components in the transfer gears or in the transmission planetary.

Problem: Aluminium particles are found.

Probable Cause:

• Worn housings, load pistons, or selector pistons in the pressure control group.

Check: Check the suction screen and the oil that is inside the torque converter updrive housing.

Illustration 5	g01081953
Lower section of the torque converter updrive housing (6) Torque converter sucton screen

Remove torque converter suction screen (6) and drain the oil from the torque converter updrive housing. Inspect the oil for foreign material. Measure the total amount of oil that is removed. Inspect the suction screen for foreign material and/or for restrictions.

Problem: More than 15 L (4.0 US gal) of oil is drained from the torque converter updrive housing.

Probable Cause:

Illustration 6	g01081951
Gear pump (transmission charging and torque converter scavenge) (3) Transmission charging pump section (4) Torque converter scavenge pump section

• Mechanical failure of torque converter scavenge pump section (4).

• Restriction in torque converter suction screen (6).

• Mechanical failure of the torque converter.

Problem: Rubber particles are found.

Probable Cause:

• Seal failure.

• Hose failure.

Problem: Iron or steel chips are found.

Probable Cause:

• Broken components in the torque converter updrive gears.

• Broken starting motor gear or flywheel gear on the engine.

Problem: Bronze particles are found.

Probable Cause:

• Worn lockup clutch in the torque converter.

Problem: Aluminium particles are found.

Probable Cause:

• Mechanical failure of the torque converter.

Check: Check the oil that is inside the transmission and the output transfer gear case.

Illustration 7	g01090350
Drain plug for the transmission and the output transfer gears

Remove the drain plug from the bottom of the output transfer gear case. This will drain all of the oil out of the transmission planetary and the transfer gears. Inspect the oil for foreign material.

Problem: Rubber particles are found.

Probable Cause:

• Seal failure.

• Hose failure.

Problem: Shiny steel particles are found.

Probable Cause:

Illustration 8	g01081951
Gear pump (transmission charging and torque converter scavenge) (3) Transmission charging pump section (4) Torque converter scavenge pump section

• Mechanical failure of torque converter scavenge pump section (4).

Problem: Bronze or black coarse material is found.

Probable Cause:

• Worn clutches in the transmission.

• Failure of a thrust disc.

Problem: Thin strands that are elastic are found.

Probable Cause:

• Worn clutches in the transmission.

Problem: Iron or steel chips are found.

Probable Cause:

• Broken components in the transfer gears or in the transmission planetary.

Problem: Aluminium particles are found.

Probable Cause:

• Worn housings, load pistons, or selector pistons in the pressure control group.

Note: If any of the particles that are listed in the checks are found during a visual check, all the components of the power train hydraulic system must be cleaned. Do not use any damaged parts. Damaged parts must be removed and new parts must be installed.