If you push down with your hand (hard) on the rear bumper, compress the rear suspension a bit, and the let off does it only come up once or does it bounce? If it bounces, or just generally bounces alot, I would replace the rear shocks.

It could also be a out of balance driveshaft, when my yoke was bent (stupid shop) it would do sorta what your saying, the vibration would be worse under deceleration compared to when your on the gas.

If its not either of those, it could be a rim bent or tire out of balance, but it would be hard to say its that since it only happens when you slow down.

 

My car is doing the same thing and i'm pretty sure its the bearings. The bearings are becoming worn out and there is slack between the ring and pinion gears. That would explain why theres on vibration when accelerating. Mineis going to cost$500 for parts and labor.

 

Mine wasn't due to the bearings....just did the rear and dropped 1200 on everything for it. It turned out being the 4 bolts that hold the yoke on the rear of the drivetrain. I talked to local sn95 guys and heard of the same problem from 3 out of 5 of them. I lost one bolt completely and the other three were barely hand tight, it was pretty close to being a disaster.

 

Has anyone heard of this before, I couldn't find a tsb on it...but didn't cobra's have this problem

 

If you end up changing out your Universal Joints, go ahead and get the ones that have grease fittings. The stock U joints on our cars don't have them. Which just seems a dumb idea in itself.