Excessive Engine Vibration at Idle (Replace Front and Rear Engine Mounts)

Some customers may comment on excessive engine vibration at idle. This vibration or resonance may cause a shaking of the rearview mirrors and the steering wheel and may also be felt in the accelerator pedal.

New engine mounting components have been developed to correct this condition. The new mounting components consist of the following items:

The new engine frame mount brackets feature a revised center hole diameter and flange thickness to accommodate the new rubber insulators. The new insulators are also being carried over to the B7 8.1L gasoline engine. No mount castings changes are required for this application.

Replace the front and rear engine mounting components on affected vehicles with the applicable new mount component part numbers listed below. Use the following procedure. Also refer to the Parts Information and RPO Definitions tables for vehicle usage information.

Notice: Broken engine mountings can cause misalignment of certain drivetrain components. Misalignment of drivetrain components causes eventual destruction of the drivetrain components. If one engine mount breaks, the rest of the engine mounts will have increased stress put on them. This could cause the rest of the engine mounts to break.

Important: On some models, the transmission rear support mount, if equipped, should be disconnected when servicing the engine mounts.

1. Open the hood or tilt the cab and secure.

Notice: When raising or supporting the engine for any reason, do not use a jack under the oil pan, any sheet metal, or the crankshaft pulley. Lifting the engine in an unapproved manner may cause component damage.

Important: When performing this service procedure, position a suitable lifting device on the engine located along each side of the engine block.

2. Install an engine lifting device.
3. Loosen, but do not remove, the four engine mount through bolts.

Engine Mount - Front (Typical)





Engine Mount - Rear (Single and Double) (Typical)




4. Remove the LH and RH front engine mount through bolts (8) and nuts (1).
5. Raise the engine providing just enough clearance to remove the engine mount.
6. Remove the RH front engine mount insulators, the engine mount frame bracket nuts and bolts, and the bracket from the frame.
7. Install the new RH front frame bracket and the bracket nuts and bolts to the frame.

Tighten
Tighten the engine mount bracket nuts to 75 N·m (55 lb ft).

8. Repeat steps 6 and 7 to replace the LH front engine mount insulators and frame brackets.

Important: Installation and final tightening of the through bolts and nuts will be completed after the weight of the engine is on the mount and the parts are centered.

9. Install the new engine mounting components including new insulators and washers.
10. Lower the engine.
11. Install, but do not tighten, the new LH and RH front engine mount through bolts and nuts.
12. Remove the engine lift.
13. Install a lifting device in order to replace the rear engine mounts.
14. Follow steps 3-12 above in order to replace the rear engine mounts.
15. Tighten the four engine mount through bolts.

Tighten
Tighten the four through bolts to 175 N·m (129 lb ft).

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use