PROM - Harsh 1-2 Shifts

File In Section: 07 - Transmission/Transaxle

Bulletin No.: 99-07-30-002

Date: February, 1999

TECHNICAL

Subject:
Harsh 1-2 Shifts (Reflash PCM Calibrations)

Models:
1999 Chevrolet and GMC C/K Models (Silverado and Sierra)
with 4.8L, 5.3L, or 6.0L Engine (VINs V, T, U - RPOs LR4, LM7, LO4) and HYDRA-MATIC 4L6O-E or 4L8O-E Automatic Transmission (RPOs M30, MT1)

Condition

Some owners may comment on a harsh 1-2 shift.

Cause

Condition may be caused by insufficient line pressure under heavy throttle.

Correction





Reflash the Powertrain Control Module (PCM) with updated calibration to soften shift. These calibrations are available on 1998 CD-ROM # 20 and later versions. Refer to your Service Manual for proper procedure.

Warranty Information

For vehicles repaired under warranty, use:

Labor

Operation Description Labor Time
Prom - Reprogramming Use published
J6355 On Car labor
operation time