| Subject: | Allison LCT1000 Harsh 3-2, 2-1 Downshift, And ABS May Activate |
| Models: | 2001-2007 Chevrolet Silverado Classic |
| 2001-2007 GMC Sierra Classic |
| Equipped With the Allison LCT1000 Transmission RPO M74, MW7 |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
The Allison LCT1000 transmission combined with 8.1 (L18) or 6.6L (LB7/LLY/LBZ/LMM) engine may experience ABS activation during a harsh 3-2 or 2-1 downshift and or harsh garage shifts. May experience delay or "hanging" upshifts when not using Tow/Haul.
The coolant temperature gauge in the IPC may read cold. The Engine Coolant Temperature Sensor (ECT) may be reading cold [approximately 15.5 degrees C (60 degrees F)] or may be reading erratic when the engine is at full operating temperature.
Recommendation/Instructions:
The ECT sensor should be monitored with the TechII Scan Tool and replaced as needed.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
