pls help! vibrating rear???

[24DSXY1]

I recently noticed my 91' 240 has a light vibrating from the rear. It doesn't feel like a warped tire or unbalanced tire kind of shaking, but a constant vibrating as if I was driving on a road covered with quarter sized reflectors, but only from the rear. I first thought it was my worn out pressure plate, but it still vibrates when rolling on neutral. Could this be from worn wheel bearings? or time to change the diff fluid(stock open diff)? or something else???

[574-240sx]

Check for worn subframe bushings or possibly an out of round tire, could even be out of balance.

[Wc240]

could also have a flat spot

[24DSXY1]

I don't think it's the tires, cause the speed of the vibration stays the same even when the car is accelerating. If it's a flat spot, it would vibrate faster when the car speeds up and vibrate slower when the car slows down.

[Wc240]

your saying the speed of the vibration is the same at 10 and 20mph as it is at 55,65, and 75mph?

[1990-240sxsr20det]

Sounds like you may be out of alignment

[24DSXY1]

yes, and even in neutral

[Wc240]

are you posative? id take it out to a good,quiet,smooth area and try to find it again.not doggin on your ability to feel but theres nothing from the transmission to the wheels that stays at a constant speed. everything speeds up with the increase of speed of the car.another thing you could check is the diff bolts. the two in front holding it up and the four in back. when they get loose, theyll do something close to what your discribing

[24DSXY1]

Okay thanks, I'll check out the diff bolts and test out different speeds again.