Buick/Olds: bonneville vibrates, cv axle, pontiac bonneville

Question
I have a 98 pontiac bonneville. It started vibrating a few months ago (over 65 mph, or going down hills. ) I thought the wheels where out of balance. Balanced them three times. I got 2 new sets of brand new tires all the way around .( and new wheels.) Balanced again . Did not help. I have been told it could be the torqe converter, motor mount, wheel bearing, cv axle, or harmonic balancer. I have paid mech. to do really nothing but say its this or that and charge me for really doing nothing. I paid over 100 bucks to flush out the transmision. No help either. It does this shaking even if I drop it in neutral and it does it weather I brake or not. (braking downhill does make it worse though)It shakes in the steering wheel and seat.It feels just like a tire is out of balance but they are not. What can this be? Thanks, Bev


Answer
Bev,
It is probably your motor mounts that are causing that problem.  It isn't anything to do with the tires because I am sure that if you accelerate in speeds over 70 MPH, the shaking will stop.  The engine smooths out and all is well.  Check for rust or signs of water entry under your hood.  That is a good indication that your mounts should probably be replaced.  A couple hundred bucks will set you straight.

Ray Barham