HIGH LINE PRESS. INSTABILITY (4L80E/4L80EHD) NEW P/N

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 9l-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 com- bination.

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

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.

SERVICE PARTS INFORMATION

Part # Description Year Model Application ------ ----------- ---- ----------------- 8683973 Pkg-Case Sub-Asm (Overseas) 1992 RAP*, RBP*, ZBP*

8683974 Pkg-Case Sub Asm (2WD) 1991 ABP, ADP, BAP, BBP, BMP, BNP, CAP, CBP, CRP, DCP, DDP, DNP, DPP, DRP, DSP

8683975 Pkg-Case Sub Asm (4WD) 1991 ACP, BJP, CKP, DLP 1992 ACP, BJP, DLP, LFP

8683976 Pkg-Case Sub Asm (Lug Cut) 1992 AFP, AJP, MBP, MKP, MPP, TSP, TWP, MHW, LAP

8680584 Plate, Valve Body Spacer 1991 ADP 1992 ABP, ACP, AJP, AFP

8680654 Plate, Valve Body Spacer 1991 BAP, BBP, BJP, BMP, BNP

8680585 Plate, Valve Body Spacer 1991 CAP, CBP, CRP, CKP 1992 BAP, BJP, BMP, BNP, LAP, LFP, LLP, MBP, MKP, JDP, MPP

8680586 Plate, Valve Body Spacer 1991 DNP, DPP 1992 DNP, DPP

8680587 Plate, Valve Body Spacer 1991 DCP, DDP, DLP, DRP 1992 DCP, DLP, DRP, TSP, TWP

8680588 Plate, Valve Body Spacer 1991 DSP 1992 HTP

8680589 Plate, Valve Body Spacer 1992 RAP*

8680590 Plate, Valve Body Spacer 1992 RBP*

8681578 Plate, Valve Body Spacer 1992 ZBP

8680583 Gasket, V.B./S.P. 1991/92 All Models

8680593 Gasket, Case/S.P. 1991/92 All Models

* Overseas Applications

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 17711OR (GMC Truck Bulletin 9l-7A-116, published August 1991) before any S.R.T.A. consideration.

Parts are currently available at GMSPO.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.