A/T - Harsh 1-2 Upshift
Bulletin Number: 92-7-20Reference Number: 277135
Publish Date: 10/92
Subject:
HARSH 1-2 UPSHIFT (INSTALL SERVICE PACKAGE)
Models Affected:
1992 FIREBIRD MODELS WITH 4L60 TRANSMISSION
TRANSMISSION MODELS: 2FTM, 2FUM, 2FZM
CONDITION: (Figure 1):
Some vehicles equipped with a 1992 HYDRA-MATIC 4L60 transmission built between Julian Date 061 (March 1, 1992) and Julian Date 171 (June 19, 1992) may experience a harsh 1-2 upshift.
NOTE:
Once the transmission is brought to operating temperature, the condition may not be able to be reproduced until a "cold soak" (overnight) is performed.
CAUSE:
The above condition may be caused due to a tapered 1-2 accumulator sleeve. The tapered bore may cause the 1-2 accumulator valve to stick in the bottom of the bore.
CORRECTION: (Figure 2)
To improve the 1-2 shift, install the service package listed in this bulletin. A 1-2 accumulator valve and 1-2 accumulator valve sleeve (which, normally, is not serviceable) is included in the package.
SERVICE PARTS INFORMATION:
Package
Number Transmission Models
8687992 2FTM, 2FUM,
8688900 2FZM
Parts are currently available from GMSPO.
SERVICE MANUAL REFERENCE:
Refer to the Hydra-Matic 4L60 unit repair section of the appropriate Service Manual for repair information.