Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1991-92 All Models (GM TSB 177119)
New friction material on 3-4 clutch plates has been installed on limited applications of Hydra-Matic 4L60 transmission. New friction material has increased heat capacity but cannot be used interchangeably with previous friction material. New material was put into production during 1991 model year. Model codes changed as transmissions received new 3-4 clutch plates.
New plates cannot be used to service any transmissions except those 1991 models listed. See 1991 TRANSMISSION MODEL LIST . Transmissions used with 5.7L engine were first to contain new plates, beginning in January 1991.
| New (1) | Previous | ||
|---|---|---|---|
| AMM | AKM | ||
| APM | DBM | ||
| CNM | CHM | ||
| CYM | CJM | ||
| FYM | FUM | ||
| KWM | KRM | ||
| LHM | None | ||
| RCM | RAM | ||
| RDM | WCM | ||
| YHM | YDM | ||
|
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NO RELATED
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.