On a club cruise on Saturday I noticed an on off vibration starting at 70 mph. It's oscillating, one second vibration, one second no vibration and it goes away at 68 mph. The tires and drive shaft are balanced and it was not there last Summer. Any ideas?

Thanks
Chuck

Vibrating through the steering wheel, body, both?

ALL of the above. The entire car get a mild vibration. This weekend I will take it on the freeway again and try to drive through it. If I get to 75 and it stops then I believe it's a ballancing problem. The strange thing is it wasn't there before. The only change to the rotating mass was a new set of 3.73:1 rear gears installed by a pro.

Chuck

Chuck,
Did you ever figure this out?

I have the same problem at about 55mph, goes away at 60mph, then a steady vibration can be felt in the pedals and seat, gets worse with speed. If I shift to nuetral or just barely lift off the gas it sometimes goes away at any speeds.
I have tried all sorts of angle changes, balanced DS twice with new u joints, tires etc

Any ideas guys?