NEW 2-4 SERVO COVER AND SEAL SERVICE INFORMATION

Model and Year ALL THM 700-R4

This cancels and replaces Chevrolet Dealer Service Information Bulletin 83-I-115 dated September, 1983 which should be destroyed. This copy includes additional means of identification of components, clarification of usage of "O" rings and additional illustrations.

Beginning April, 1983, all THM 700-R4 transmissions were built with a new 2-4 servo cover and seal. This change provides a tighter fit between the case servo bore and the 2-4 servo cover.

The new servo cover "O" ring (P/N 8647351) is identified with a green stripe. This is to distinguish it from the past "O" ring (P/N 8642112) which is still used on the second apply piston (refer to Figure 2, numbers 14 and 21 for correct location of "O" rings).

NOTICE: The past servo "O" ring (P/N 8642112) cannot be used with the new servo cover, if used together they will leak.

SERVICE INFORMATION

If a leak is found at the 2-4 servo cover:

1. Remove the 2-4 servo cover and "O" ring seal.

2. Check the case servo bore f or sharp edges especially at the recessed slots (see Figure 1).

3. Check the case servo bore for burrs, nicks and damage on sealing wall. If damage is found replace the case.

4. Check the 2-4 servo cover for porosity or damage. If required replace with P/N 8642979 which will contain a new 2-4 servo cover and "O" ring seal.

5. If it is necessary to replace only the "O" ring seal, use P/N 8647351.

6. When installing the 2-4 servo cover and "O" ring seal, lubricate the seal with petrolatum or equivalent and use care not to cut the seal during installation.

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.