1989 - 1991 Corvette: Service Bulletin: No/Delayed Reverse When Cold

Subject: NO/DELAYED REVERSE WHEN COLD INSTALL REV. INPUT CLUTCH SEAL
Model and Year:
1989-91 CAPRICE CAMARO AND CORVETTE
1989-91 C/K, R/V, S/T, G AND M TRUCKS
1990 L TRUCKS WITH 4L60 AUTOMATIC TRANSMISSION
Source: Chevrolet Service Bulletin
Bulletin Number: 91-493-7A - (03/11/1992)

TRANSMISSION APPLICATION:

1989-91 HYDRA-MATIC 4L60 (MD8)

TRANSMISSION MODELS:

All

SUBJECT: ------- No Reverse/Delayed Reverse Cold (Install Long Lipped Reverse Input Clutch Piston Outer Seal)

VEHICLE APPLICATIONS:

B, F, Y, - Cars C/K, S/T, RV - Trucks G, L, M - Vans

Bulletin Covers:

Some 1989-1991 HYDRA-MATIC 4L60 (THM 700-R4) transmissions may exhibit a ’no reverse’ or ’delayed reverse’ condition when outside temperatures are below zero degrees Fahrenheit.

Service Information:

A transmission is considered to have a delayed reverse condition if it takes longer than three seconds for the transmission to engage when shifted into the reverse range.

If a transmission has a ’no reverse’ or ’delayed reverse’ condition, inspect the reverse input clutch piston outer seal. Determine if the seal is a ’short lip’ or ’long lip’ design by comparing it to Figure 1. If it is a short lip design, replace it with a long lip seal contained in the service packages listed under Service Parts Information.

If the reverse input clutch piston outer seal is a long lip design, or the newly installed long lip seal doesn’t alleviate the delayed reverse condition, the reverse input clutch housing may be out of round. Inspect the housing and replace if necessary.

Service Parts Information:

The long lipped seals are available in several service packages. Description Part Number

----------- -----------

Pkg - Overhaul Seals and Gaskets 8683958

Pkg - Overhaul Repair Complete 8683959

Parts are available at GMSPO.

Service Manual Reference:

Refer to the HYDRA-MATIC 4L60 Automatic Transmission Unit Repair Section of the appropriate Service Manual for instructions on installing the reverse input clutch seals.

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.