Suburban 1/2 Ton 4WD V8-305 5.0L (1986)
Valve Body: All Technical Service Bulletins
A/T - 4L60 Binding/Inoperative In Reverse
Number:
91-283-7A
Section:
7A
Date:
APRIL 1991
Corp. Bulletin No.: 977143R
Subject:
BINDING OR INOPERATIVE IN REVERSE - STUCK 4-3 SEQUENCE VALVE AND/OR 2-3 SHIFT VALVE
Model and Year:
1982-91 PASSENGER CARS AND TRUCKS WITH 700R4 (4L60) AUTOMATIC TRANSMISSION
THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO. 89-271-7A, DATED OCTOBER 1989. THE 1990-91
MODEL YEARS HAVE BEEN ADDED, AS WELL AS INFORMATION CONCERNING BOLT TIGHTENING PATTERN. ALL COPIES OF
89-271-7A SHOULD BE DISCARDED.
Figure 1 - Control Valve Assembly
SERVICE PROCEDURE:
When servicing a HYDRA-MATIC 4L60 transmission for a binding in reverse condition, remove the control valve assembly and inspect the 4-3
sequence valve and the 2-3 shift valve. Refer to Figure 1. Either valve, if stuck in the upshifted position, will result in a binding condition. To correct this
condition, the valve body must be completely disassembled and reconditioned according to procedures contaihed in the HYDRA-MATIC 4L60/THM
700-R4 Unit Repair section of the appropriate Service Manual.
Inspect the transmission bottom pan for clutch material or burned fluid. Evidence of this will necessitate further transmission diagnosis. Repairs may
include complete transmission reconditioning, inc.luding disassembly and reconditioning of the transmission pump and possible torque converter
replacement.
Complete the cleaning of the hydraulic circuit by changing the transmission fluid and filter and flushing the transmission cooler and cooler pipes.