C 1500 Truck 2WD V8-350 5.7L (1989)
Vibration Damper: All Technical Service Bulletins
Brakes, Rear - Moan or Howl Noise Upon Applications
Number:
90-411-5
Section:
5
Date:
March 1991
Corp. Bulletin No: 065023
Subject:
REAR BRAKE NOISE MOAN/HOWL
Model and Year:
1988-90 C3 AND K3 TRUCKS WITH SINGLE REAR WHEELS
Some owners of 1988-90 C3 and K3 light duty trucks may experience a moan or howl noise upon brake applications. The noise may be more noticeable
at low speeds nearing the end of the stop.
The noise is caused by normal brake drum vibrations causing the rear brake backing plates to oscillate at their resonant frequency. The noise will not
damage any of the vehicle components.
To correct this condition, the rear axle assemblies on C3 and K3 trucks have been modified to change the resonant frequency.
VEHICLES INVOLVED
Vehicles built after the following breakpoints have the new axle assemblies installed in assembly:
VIN
PLANT
1GCGK34N6LE244095
PONTIAC EAST ASSEMBLY
2GCGC39N6L1252916
OSHAWA TRUCK ASSEMBLY
Vehicles from Fort Wayne Assembly are not affected by this change as Fort Wayne does not build the C3 or K3 series vehicles.
SERVICE PROCEDURE:
To correct this condition, in service a tuned dampener assembly has been developed. When installed at the rear leaf spring "U" - Bolts the dampener will
oscillate 180 degrees out of phase with the resonant frequency effectively eliminating the generation of the noise.
