2ND REDUCTION FINAL DRIVE BEARINGS MAY FAIL PREMATURELY

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2ND REDUCTION FINAL DRIVE BEARINGS MAY FAIL PREMATURELY

CONFIDENTIAL TIBU2688-00

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TECHNICAL INFORMATION BULLETIN	NOVEMBER 26, 2003
OFF-HIGHWAY TRUCKS	784C (2PZ1-UP), 785C (APX180-UP), 785C HAA (5AZ400-UP) 789C (2BW337-UP), 793C (ATY535-UP), 793C XQ (CBR94-UP), 797 (5YW1-UP), 797B (JSM1-UP)
COMPONENT CODE	4001, 4050

SUBJECT: 2^ND REDUCTION FINAL DRIVE BEARINGS MAY FAIL PREMATURELY

PROBLEM:

The sub-surface hardness of 225-8578 Bearing may not meet specifications. Failures of the new 225-8578 Bearing, used in the 793 Off-Highway Truck 2^nd reduction final drive, have been reported from the field. Although there have been no recorded failures of the 225-8577 Bearing, used in the 785/789 second reduction final drive, or the 225-8579 Bearing, used in the 797 second reduction final drives, the same sub-surface conditions may exist. The initial indication of failure has been metal on the final drive magnetic plug. If the truck is allowed to continue operating under this condition, micro welding of the bearing roller and race progresses into severe spalling and final failure of the planet bearing.

Affected 784C, 785C, and 789C Trucks:

The new 225-8577 bearings were installed in the factory on 785 (APX00371-Up) and 789 (2BW00611-Up). In addition to these trucks, any final drive that was rebuilt using the new 225-8577 bearings is also affected.

Affected 793C Trucks:

The new 225-8578 Bearing was factory installed on 793C (ATY555-Up) and 793C XQ (CBR94-Up). In addition to these trucks, any final drive that was rebuilt using the new 225-8577 bearings is also affected.

Affected 797 and 797B Trucks:

There are no factory installed 225-8579 Bearings. Any final drive that was rebuilt using the new 225-8579 Bearing is affected.

SOLUTION:

Check the magnetic plugs for signs of metal generation. Also review the final drive oil samples for iron levels. If the oil samples are showing iron levels of 150 parts or above, the truck should be taken down for a comprehensive visual inspection of the 2nd reduction final drive and bearings replaced if needed.

At this time we are recommending that none of the 225-8577 Bearings, 225-8578 Bearings, & 225-8579 Bearings in dealer stock be used for rebuild replacement in trucks unless it is for a machine down condition.

We are in the process of resolving this heat treat issue and intend to have replacement parts available in the next few weeks. The three existing part numbers (225-8577, 225-8578 & 225-8579) will be canceled and replaced by new part numbers, which will be communicated, as the new parts are available.

Note: Existing quantities of 225-8577 Bearings, 225-8578 Bearings, and 225-8579 Bearings that are currently in Morton are currently on freeze hold and will only be released for dealer orders under a Mega order (machine down in the field). Trucks with any of the three bearings listed above found to have indications of metal on the magnetic plugs or high iron count in the oil samples exceeding a particle count of 150, that have verification of bearing failure through visual inspection, should have the bearings changed out and ordered under the Mega condition.