Beretta V6-173 2.8L (1989)
Suspension Spring ( Coil / Leaf ): All Technical Service Bulletins
Engine - Vibration Felt At Idle and In Park
Number:
91-378-4D
Section:
4D
Date:
JULY 1991
Corporate Bulletin No.: 137103R
Subject:
DRIVE LINE IDLE AND/OR PARK VIBRATION
Model and Year:
1988-91 CORSICA OR BERETTA WITH 2.8L OR 3.1L ENGINE AND AUTOMATIC TRANSMISSION
Model and Year:
1988-91 "L" cars with 2.8L (VIN W, RPO LB6), or 3.1L (VIN T, RPO LHO), 125C or 3T40 (RPO MD) Automatic Transaxle and
FE1 Front Suspension.
Some customers of the above specified Corsica/Beretta may experience a vibration felt from the seat, floor, and/or steering wheel with the engine at idle
and the vehicle in gear. The vibration may also be described as a noise or boom and could be more noticeable with the vehicle on an incline with the air
conditioning operating, and/or with the vehicle in park.
It has been found that this condition could be a third order engine vibration (firing frequency) being transmitted through the drive axles into the
passenger compartment from the steering linkage and suspension.
When attempting to diagnose this condition, the following preliminary items should be checked first:
1. Inspect the engine and transaxle mounts for grounding or binding. Loosen the mounts, start engine and run at idle. Shift the engine through its gear
ranges, then tighten the engine mounts to 67 N-m (50 lbs.ft.).
2. Inspect the exhaust system for grounding and align as required.
If either of the two preliminary checks listed above do not repair the vibration condition, replace BOTH cross-groove type drive axles with the newer
designed tri-pot ("free-motion") type drive axles. Due to their design, the cross-grove type drive axle could act as a direct transmitter of the engine
vibration. The tri-pot ("free-motion") drive axle has the ability to translate axial (in and out) motion in its housing and not transmit much of the vibration.
Refer to Service Parts Information in this bulletin for the proper drive axle replacement part numbers. For the proper removal and installation procedure,
refer to Drive Axle (Section 4D) of the Corsica/Beretta Service Manual. Warranty information is listed at the end of this bulletin.
If a "launch shudder" or wobble on wide open throttle acceleration is felt after installing the tripot (free-motion) axles, the front end trim height should be
measured and adjusted. Lowering (reducing) the vehicle trim height may reduce the shudder condition to an acceptable level. The front end trim heights
may be adjusted by replacing the front coil springs with the next lower load springs. Each spring rate, listed in the Spring Chart in the
Parts Catalog, lowers the vehicle approximately 13.0 mm (0.5 in.). After BOTH new springs (LH and RH) are installed, the vehicles trim height must be
remeasured to assure that the trim heights have been decreased.
For the proper front coil spring part numbers, refer to the Spring Charts in the Parts Catalog. To check vehicle trim height, refer to Steering, Suspension,
Tires and Wheels Diagnosis (Section 3) of the Corsica/Beretta Service Manual. For the coil spring removal and installation procedure, refer to Front
Suspension (Section 3C) of the Corsica/Beretta Service Manual.
Service Parts Information
Part Number
Quantity
Description
26015000
1
RH Front Drive Shaft Kit
26015026
1
LH Front Drive Shaft Kit
Parts are currently available from GMSPO.
For the recommended proper front coil spring part numbers, refer to the Spring Charts in the Parts Catalog.
Warranty Information:
Labor Operation Number:
T1737
Labor Time:
Trouble
Code