A/T - Harsh 1st to 2nd gear Upshifts
FILE IN SECTION: 7 - TransmissionBULLETIN NO.: 57-71-04
DATE: February, 1995
SUBJECT:
Harsh 1-2 Upshifts (Service Procedure)
MODELS:
1993-95 Buick Regal
1993-95 Chevrolet Lumina
1995 Chevrolet Monte Carlo
1993-95 Oldsmobile Cutlass Supreme
1993-95 Pontiac Grand Prix
with 3.1 L Engine (VIN M - RPO L82) and Hydra-Matic 4T60-E Transaxle (RPO M13)
CONDITION
Some owners may notice a harsh 1-2 upshift condition. The harsh upshift condition will usually be noticeable during a light to medium throttle upshift.
CAUSE (Figures 1 and 2)
The harsh 1-2 upshift may be caused by one of the following:
^ A binding 1-2 accumulator piston in the accumulator housing.
^ A missing or loose accumulator bushing retainer.
^ A metal shaving (burr) or debris in the 1-2 accumulator secondary valve train in the control valve body.
Important:
3BHW, 4AFW and 5AFW models have a 1-2 accumulator primary valve train and 1-2 accumulator piston/spring line up that is different from most 4T60-E models. Do not assume that these models have a harsh shift condition due to misassembly. Figures 1 and 2 correctly show the 1-2 accumulator components for these models. The 1993 and 1994 Service Manual Section 7A-5B is incorrect. The 1995 Service Manual Section 7A-5B does correctly show the 1-2 accumulator components.
CORRECTION (Figures 1 and 2)
To repair this condition, perform the following procedure:
1. Remove and disassemble the 1-2 and 2-3 accumulator housing assembly and inspect for the 1-2 accumulator piston being stuck or binding in the bottom of the accumulator bore.
^ If the accumulator piston is stuck in the bore, replace the accumulator housing. Refer to SERVICE PARTS INFORMATION.
^ Refer to the appropriate Service Manual for specific repair procedures.
2. If the 1-2 accumulator was not stuck in the accumulator housing, remove the control valve body and inspect for a missing retainer on the 1-2 accumulator primary or secondary valve bushing assemblies.
^ Replace any missing retainers. Refer to SERVICE PARTS INFORMATION.
^ Refer to the appropriate Service Manual for specific repair procedures.
3. If the 1-2 accumulator primary or secondary valve bushing assemblies were not missing a retainer, disassemble the 1-2 accumulator primary and secondary valve and bushing assemblies and inspect for a binding or stuck valve due to sediment or burrs.
^ Clean the control valve body if burrs or debris are found.
^ If the valve or bushing are damaged beyond repair, replace the control valve body assembly. Refer to SERVICE PARTS INFORMATION.
^ Refer to the appropriate Service Manual for specific cleaning and control valve body repair procedures.
PARTS INFORMATION (Figures 1 and 2)
P/N DESCRIPTION
8677163 Housing - Accumulator (item 140)
8681510 Retainer - Accumulator Bushing,
3/package (item 385)
24200845 Body Assembly - Control Valve,
3BHW, 4AFW, 5AFW (item 301)
Parts are currently available from GMSPO.
WARRANTY INFORMATION
For vehicles repaired under warranty requiring only step 1 of the SERVICE PROCEDURE to be performed, use:
LABOR
OPERATION LABOR TIME
K6507 Use the published labor operation time.
For vehicles repaired under warranty requiring steps 1 and 2 or all three steps of the SERVICE PROCEDURE to be performed, use:
LABOR
OPERATION LABOR TIME
K6570 Use the published labor operation
time plus an add time of 1.0 hr