G 2500 3/4 Ton Van V8-6.5L DSL Turbo VIN F (1996)
Shift Solenoid: Customer Interest
A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling
File In Section: 7 Transmission
Bulletin No.: 77-71-77
Date: December, 1997
Subject:
Loss of 4th Gear, Slipping in 4th Gear, Busy 3-4 Shifting or TCC Cycling
(Replace Shift Solenoids)
Models:
1996-97 Chevrolet and GMC C/K, G, P Models
with HYDRA-MATIC 4L8OE Transmission (RPO MT1)
Condition
Some owners may comment about a loss of 4th gear, slipping in 4th gear, busy 3-4 shifting or Torque Converter Clutch (TCC) cycling and no DTC's are
setting.
Cause
Shift solenoid leaking hydraulically.
Correction
If normal diagnosis does not provide a correction, follow the solenoid test procedure listed. Replace the shift solenoid if it fails the test. Also verify that
the transmission cooling system is operating properly.
Service Information (figure 1)
Starting June 23, 1997 (Julian date 174) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids
will service all 1991 through 1997 4L80-E applications.
The above listed conditions occur mainly on high duty cycle applications and/or when the transmission is operated under high temperature conditions.
Each solenoid may be tested for leaking using the following test:
