G 30 Van V8-454 7.4L VIN J SFI (1996)
PROM - Programmable Read Only Memory: All Technical Service Bulletins
A/T - Clunk Noise On Acceleration After Coast Down
File In Section: 7 - Transmission
Bulletin No.: 67-71-59
Date: February, 1997
Subject:
Clunk Noise on Acceleration After a Closed Throttle Coast Down
(New TCC Calibration)
Models:
1996 Chevrolet and GMC C/K, P Trucks, G Van
with 7.4L Engine (VIN J - RPO L29) and HYDRA-MATIC 4L8OE Transmission (RPO MT1)
Condition
Some owners may comment about a clunk noise on acceleration after a closed throttle coast down.
Cause
Driveline clunk is transmitted through the vehicle with the Torque Converter Clutch (TCC) applied. The PCM/VCM software calibration maintains TCC
application at closed throttle. The TCC release is based on vehicle speed and the brake switch inputs.
Correction
If normal diagnostics do not lead to a resolution, reflash the PCM/VCM with the appropriate part number listed below. The new software calibration will
allow the TCC to release at the closed throttle position. The new software calibration will be available with CD ROM 1996 Disc # 22 from GM Service
Technology Group.
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 File
Number Version
16227602
CD ROM 1996 Disc 22
16227603
CD ROM 1996 Disc 22
16227604
CD ROM 1996 Disc 22
16227605
CD ROM 1996 Disc 22
This new calibration will be available starting 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.
