| Subject: | No Movement When Transmission is Shifted to Drive or Third -- Normal Operation When Shifted to Second, First or Reverse (Replace Forward Sprag Assembly) |
| Models: | 1982-2005 GM Passenger Cars and Light Duty Trucks |
| 2006 Cadillac Escalade, Escalade ESV, Escalade EXT |
| 2006-2008 Chevrolet Avalanche, Colorado, Express, Silverado Classic, Silverado, Suburban, Tahoe, TrailBlazer |
| 2006 GMC Yukon Denali, Yukon Denali XL |
| 2006-2008 GMC Canyon, Envoy, Savana, Sierra Classic, Sierra, Yukon, Yukon XL |
| with 4L60, 4L60E, 4L65E or 4L70E Automatic Transmission (RPOs MD8, M30, M32, M33 or M70) |
Condition
Some customers may comment that the vehicle has no movement when the transmission is shifted to DRIVE or THIRD position, but there is normal operation when it is shifted to SECOND, FIRST or REVERSE position.
Cause
This condition may be caused by a damaged forward sprag assembly (642).
Correction
When inspecting the sprag, it is important to test the sprag for proper operation by holding the outer race (644) with one hand while rotating the input sun gear (640) with the other hand. The sun gear should rotate only in the counterclockwise direction
with the input sun gear facing upward. If the sprag rotates in both directions or will not rotate in either direction, the sprag elements should be inspected by removing one of the sprag assembly retaining rings (643). Refer to SI Unit Repair section for forward
clutch sprag disassembly procedures.
If the sprag is found to be damaged, make repairs to the transmission as necessary. A new forward roller clutch sprag assembly is now available from GMSPO.
If clutch debris is found, it is also very important to inspect the Pressure Control (PC) solenoid valve (377) fluid screens. Clean or replace the PC solenoid (377) as necessary. It is also important to flush and flow check the transmission oil cooler
using J45096. Refer to SI Automatic Transmission Oil Cooler Flushing and Flow Test for the procedure.
