I have recently purchased a 2000 Bonneville SLE with 85k miles. It runs
smooth normally but when I put it in reverse to back out of my garage
the engine seems to transmit a lot of vibration through the chassis.
For example the dash rattles internally and the steering wheel seems to
vibrate - it just seems harsh. My 2000 Grand Prix does not do this.
Could there be motor or transmission mounts that fail over time
resulting in the engine or drive train grounding to the chassis under
certain load conditions? Any other things to check?

You need to put it up on a hoist, power brake it in reverse and look for
the ground out.

Also watch the mounts for excessive movement.


"DJ" <djandsj (AT) charter (DOT) net> wrote

johnoz19 wrote:
at only 85k miles?

That does seem quite early to go bad. I would guess something in the
line of a bent exhaust or missing exhaust hangers. Look for after market
parts installed wrong.

Instead of a hoist, put it up on ramps and go under. Then have someone
you trust power brake it. Watch you don't burn your nose. Most of the time
it's the exhaust hitting a heat shield or the down pipe making contact with
the tunnel.