Bump old thread because my car is doing the exact thing as OP. Has nothing to do with braking, if accelerating at high speeds, car is smooth sailing, as soon as I let off the gas car shakes. Feels like it's coming from the rear and almost like an unbalanced tire. But if it was tire, it would shake at speed no matter what (I've had that problem before), this really only happens when decelerating at interstate speed (75-80 mph).

 

We can look in to this tomorrow when I get there.

 

As mentioned in my reply, get your rims checked. I had a bent rim that was on the inside of the wheel and that's what caused it to shake when I decelerate.

 

I noticed the exact same thing on my trip through the mountains this weekend...only when i would let off the gas would it vibrate. even the slightest push of the go pedal and it would be smooth as silk...

really would like to know what is causing this...hopefully its just an easy fix becuase i dont feel like dumping money into a vehicle i just bought

 

Next step will be to try changing out my rear wheels. Just to confirm, did replacing your bent wheel fix this problem for you?

PAIXAO suggested I put the car in neutral, and it still shook but definitely was isolated to the rear. If it's not a bent rim, I'm going to start checking bushings.

 

Rims look good, but I noticed this when I had the car jacked up o_O








Strong hunch this might be my problem. Apparently the rear differential bushing is filled with liquid and it ruptured.