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.
This condition may be caused by a damaged forward sprag assembly (642).
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.
The following information applies when this sprag is used in 1982-86 transmissions.
The new design sprag can be used on models 1982 through 1986, by replacing the entire assembly (637 -- 644). Individual components are NOT interchangeable.
Important: The wear plate (640) and input thrust washer (660) are not required with the new sprag. Use of the thrust washer and wear plate with the new sprag assembly will cause a misbuild (correct end play cannot be obtained).