Interior - Vibration In Seat & Steering Wheel

GMC NUMBER: 92-6A-96

GROUP: 6A Engine Mechanical

DATE: June 1992

CORPORATE
NUMBER: 266102



SUBJECT:
VIBRATION IN SEAT AND STEERING WHEEL (MODIFY RIGHT ENGINE MOUNT)

MODELS:
1988-92 "C" TRUCKS WITH 4.3L ENGINE (RPO LB4)









Some owners of 1988-92 C trucks with 4.3L engines may comment about a vibration felt in the seat and steering wheel during the first few seconds of acceleration from a stop. This condition may be caused by the right front engine mount housing (Figure 2) contacting the bracket which supports the engine mount. This bracket is part of an assembly which is bolted to the frame (Figure 1).

Note:
ONLY the right engine mount is affected. Modification of the engine mount provides more clearance between the metal mount housing and the frame bracket.

SERVICE PROCEDURE

1. Mark the area of the bracket assembly which surrounds the right front engine mount with white detection powder (foot powder may be used).

2. Test drive the vehicle. Make 3-5 short accelerations from a stop so that the vibration occurs.

3. If witness marks occur on the bracket in front of the mount, remove the mount (steps 4-7). If no witness marks occur, refer to the appropriate Service Manual; Section 0C "VIBRATION DIAGNOSIS" for further diagnosis.

4. Remove the right side engine mounting through-bolt and nut.

5. Raise the engine only enough to permit removal of the engine mount from the engine.

6. Remove the three mounting assembly bolts.

7. Remove the right side mount assembly.





8. Remove, with a bench grinder or other suitable tool, 6 mm (15/64 in.) from the front side of the lower part of the curved mount housing (Figure 2).



Caution:
Eye protection must be worn when using a grinder.

Important

Do not remove any more than 6 mm (15/64 in) of metal from the mount as it may cause the mount to be too weak.

9. Install the engine mount and the three mounting assembly bolts. Torque the bolts to 51 N-m (38 lbs.ft.)

10. Lower the engine until the through-bolt can be inserted.

11. Install the engine mount through-bolt and nut and torque to 95 N-m (70 lbs.ft.).

Important

Do not perform the service fix to 1993 trucks. Removing 6 mm (15/64 in.) from the mount of one of these vehicles, will decrease the strength of the mount to an unacceptable level.

Installing a new mount will not repair the vehicle.





Warranty Information

For vehicles repaired under warranty use.