A/T - Undesired 3-2 Down Shift Point
File In Section: 7 - TransmissionBulletin No.: 77-71-63
Date: June, 1997
Subject:
Undesired Transmission Down Shifting Between Third and Second Gear When Manually Shifted to First Gear (D1) (New Calibration)
Models:
1997 Chevrolet and GMC G Models with 4.3L Engine (VIN W - RPO L35) and a HYDRA-MATIC 4L80E Automatic Transmission (RPO MT1) On Vehicles built from S.O.P. through VIN V1018583
Condition
Some owners may comment on a condition in which a desired downshift between third and second gear does not occur until approximately 40 mph (64 kmph) when shifted manually into first gear (D1).
Cause
Some vehicles were built with an improper transmission downshift speed calibration when manually shifted into first gear (D1).
Correction
Reflash the VCM with the appropriate part number listed below.
Service Information
Do not attempt to order the software/calibrations from GMSPO. They are programmed into the vehicle's PCM/VCM via a Techline Tool Device.
Parts Information
New Calibration File Number Version
16216189 CD ROM 1996 DISC 22
This new calibration is available with the CD ROM 1996 Disc 22 Update.
Warranty Information
For vehicles repaired under warranty, use:
Labor Operation Labor Time
J6352 OFF-CAR Use published labor
J6355 ON-CAR operation time