A/T - High Line Pressure Instability

9214chevy02

GMC NUMBER: 92-7A-36

GROUP: 7A Automatic Transmission

DATE: January 1992

CORPORATE
NUMBER: 177128


SUBJECT: HIGH LINE PRESSURE INSTABILITY (NEW SPACER PLATES AND GASKETS)

MODELS: 1991-92 C/K AND R/V/P/G MODELS WITH 4L80-E/4L80-EHD


THIS BULLETIN IS IN CONJUNCTION WITH CORPORATE BULLETIN # 177110R, GMC TRUCK BULLETIN 91-7A-116, PUBLISHED AUGUST 1991.


Some HYDRA-MATIC 4L80-E/4L80-EHD transmissions may experience high line pressure instability caused by the pressure regulator valve spring combination.

New spacer plates and gaskets were released to correct the instability. Refer to the appropriate service manual section for proper replacement procedures.





SERVICE PARTS INFORMATION:

Figure 1:

Production Date: (Figure 1) Starting August 21, 1991 (Julian Date 233) all HYDRA-MATIC 4L80-E/4L80-EHD transmissions were built with the new spacer plate and gaskets.


Important

ALL NEW SPACER PLATES AND GASKETS MUST BE USED TOGETHER.

New plates and gaskets must be used with the new case to improve stability.


New plates and gaskets can be used with old case and will function, but will not improve stability.

To improve stability on units built prior to Julian Date 233, reference Corporation Bulletin 177110R (GMC Truck Bulletin 91-7A-116, published August 1991) before any S.R.T.A. consideration. Parts are currently available at GMSPO.