A/T - 4L60 Binding/Inoperative In Reverse

91chevy13

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.

HYDRA-MATIC 4L60:

IMPORTANT:
Overtorquing or uneven torquing of the bolts during unit reassembly can cause valves to bind. This condition may become more apparent as the unit warms to operating temperature. The correct bolt torque specifications for the HYDRA-MATIC 4L60 control valve assembly are 8-14 N-m (6-10 lb.ft.). Torquing bolts to the minimum specification, 8 N-m (6 lb.ft.) is recommended. The bolts should be tightened in a spiral pattern starting at the center and working toward the outside of the control valve assembly as shown in Figure 2.