K 1500 Truck 4WD V6-262 4.3L (1991)
Fluid Pump: Customer Interest
A/T - 4L80E/4L80EHD Buzz/Vibration
Number:
91-348-7A
Section:
7A
Date:
JUNE 1991
Corporate Bulletin No.: 177110R
Subject:
BUZZ OR VIBRATION NOISE IN PARK OR NEUTRAL
Model and Year:
1991 C, K, R, V, G TRUCKS WITH 4L80E/4L80EHD AUTOMATIC TRANSMISSION
SERVICE INFORMATION:
Some HYDRA-MATIC 4L80-E/4L80-EHD Transmissions may experience a buzz or vibration noise while in park or neutral. This is caused by line
pressure instability in the pressure regulator valve line-up. Changes made to the Pump Assembly will eliminate this condition. A service package is
released for an on-vehicle correction to the Pressure Regulator Valve lineup in the Pump Assembly.
Figure 1 - HYDRA-MATIC 4L80-E/4L80-EHD Transmission Identification Information.
DATE OF PRODUCTION CHANGE: (Figure 1)
Starting March 15, 1991 (Julian Date 074) all HYDRA-MATIC 4L80-E/4L80-EHD models were built with the new Pressure Regulator and Reverse
Boost Valve assembly.
SERVICE PARTS INFORMATION:
Part Number
Part Description
8682998
Package, Pressure Regulator and
Reverse Boost Valve
Parts are currently available from GMSPO.
Pump cover and Body Assemblies will have new numbers with updated parts at a future date.
