Transmission May Not Downshift Correctly Caterpillar

Transmission May Not Downshift Correctly

Usage:

Off-Highway Trucks785B (6HK),
789B (7EK),
793B (1HL),
793C (4AR) OFF-HIGHWAY TRUCKS

Problem:

VIMS equipped Off-Highway Trucks using the 160-7557 Control Group (EPTC-II Transmission Control) may not downshift correctly when transitioning to an uphill grade after traveling in 5th or 6th gear. Some trucks have experienced the transmission downshifting only 1 or 2 gears. This has been identified as a software problem related to the new 160-7557 Control Group when used in large Off-Highway Trucks only.

Solution:

Until a permanent fix is available, momentarily applying the Service Brakes or Retarder will allow the transmission to downshift normally.

Effective: 785B (6HK874, 6HK887-UP), 789B (7EK654-657, 7EK674-UP), 793C (4AR154, 4AR220-221, 4AR257, 4AR329, 4AR336-UP). The 160-7557 Control Group replaces former part numbers 159-0637, 146-5821 and 138-7387 and may have been used as repair/replacement parts on other Off-Highway Trucks.

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