HARSH 1-2 UPSHIFT INSTALL SERVICE PACKAGE

SUBJECT: HARSH 1-2 UPSHIFT (INSTALL SERVICE PACKAGE)

VEHICLES AFFECTED: 1992 "B, D, F, Y" MODELS; "C/K, S/T" TRUCKS; "G, L, M" VANS WITH 4L60 TRANSMISSION

TRANSMISSION APPLICATIONS:

1992 HYDRA-MATIC 4L60 TRANSMISSION MODELS:

2AAM 2ACM 2ADM 2AKM 2BAM 2BBM 2BCM 2BHM 2BRM 2BWM 2CAM 2CBM 2CCM 2CFM 2CHM 2CJM 2CPM 2FTM 2FUM 2FZM 2HBM 2HDM 2HLM 2KHM 2KJM 2KMM 2LHM 2MDM 2MJM 2MSM 2SHM 2TAM 2TBM 2TLM 2TWM 2WAM 2WBM 2WCM 2YAM 2YCM

CONDITION:

--------- 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. (Figure 1)

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:

---------- 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. (Figure 2)

SERVICE PARTS INFORMATION:

Package Number Transmission Models ------- ------------------- 8687992 2AAM 2ACM 2BAM 2BBM 2BCM 2BHM 2BRM 2BWM 2CAM 2CBM 2CCM 2CFM 2CHM 2CJM 2FTM 2FUM 2HBM 2HLM 2KHM 2KJM 2KMM 2LHM 2MJM 2SHM 2TLM 2TWM 2WAM 2WBM 2WCM

8688900 2ADM 2AKM 2CPM 2FZM 2HDM 2MDM 2MSM 2TAM 2TBM 2YAM 2YCM

SERVICE MANUAL REFERENCE:

Refer to the HYDRA-MATIC 4L60 Unit Repair Section of the appropriate service manual for repair information.

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.