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

Subject: HIGH LINE PRESSURE INSTABILITY

Model and Year: 1991-92 C/K, R/V, P, G MODELS WITH 4L80-E/4L80-EHD -----------------------------------------------------------------------------

TRANSMISSION APPLICATIONS:

1991-92 HYDRA-MATIC 4L80-E/4L80-EHD

TRANSMISSION MODELS:

All Models

SUBJECT: -------- High Line Pressure Instability (New Spacer Plates and Gaskets) Service Information

VEHICLE APPLICATIONS:

C/K, R/V, and P - Trucks G - Van

(This bulletin is in conjunction with Dealer Service Bulletin No. 91-348-7a, dated June 1991.)

Condition:

----------- Some HYDRA-MATIC 4L80-E/4L80-EHD transmissions may experience high line pressure instability.

Cause:

------- This instability is caused by the Pressure Regulator valve spring combination.

Correction:

------------ New Spacer Plates and Gaskets were released to correct the instability.

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

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

8683974 Pkg-Case Sub Asm (2WD) 1991 ABP, ADP, BAP, BBP, BMP, BNP, CAP, CBP,

CRP, DCP, DDP, DNP, DPP, DRP, DSP 1992 ABP, BAP, BMP, BNP, DCP, DRP, DNP, DPP, HTP, LLP, JDP

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, MHP, LAP

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

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

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. All 1991/1992 Models

8680593 Gasket, Case / S.R All 1991/1992 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 instability.

New Plates and Gaskets can be used with old case and will function, but will not improve instability

To improve instability on units built prior to Julian Date 233, reference Dealer Service Bulletin No. 91-348-7A before any S.R.T.A. consideration.

Parts are currently available from GMSPO.

Service Manual Reference:

Refer to the appropriate Service Manual Section for proper replacement procedures.

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.