Rhythmic thrumming vibration at 50-55+ mph

[VANILLA_GORILLA]

I have this rhythmic thrumming vibration driving past 50-55 mph. You can feel it in the steering wheel and, well, the entire car. Seems to go away when I let off the gas and come back when I get back on the gas. Any ideas?

Edit/Update: I just moved the car to wash her and the same rhythmic thrumming vibration (though slightly less felt) can be felt with the car in park and holding the engine to a certain rpm (feels about the same rpm as cruising at 50+ mph). I have no tach, so I cant be sure. This is with the car in park and not moving at all, so the driveshaft wouldnt be spinning. Any ideas now?

BTW, I'm not sure how the trans mount looks, and recently I changed the drivers side motor mount because it broke, but did not change the passenger side motor mount. The passenger side motor mount and trans mount are original to the car. The vibration was being felt prior to and after changing the motor mount...

[horsehead]

I would start with the U-joints---

[Fullbasement]

Drive train. If the u joints aren't new, go ahead and replace them. If it still persist after that, check the drive shaft angle at the rear end and at the transmission. They should be equal and opposite.

[bartl]

Front u-joint, most likely.

[VANILLA_GORILLA]

Is replacing ujoints something I can do myself In my garage?

[quicknick_2]

I had a drive shaft throw a weight once. Check it while you are examining the u-joints.

[VANILLA_GORILLA]

Didn't seem like this problem arose until after I got the car back from a tranny fluid drain and refill.

If a weight fell off how could I tell. I don't know what to look for.

[slim]

Did this start recently? If so have you replaced or changed something in the drive train (including wheels or tires).


Slim

[bartl]

Originally Posted by VANILLA_GORILLA

Is replacing ujoints something I can do myself In my garage?

Absolutely.

How to Change the Universal Joint in a Mustang | eHow.com

Looks like it's meant for a newer model, but basically the same.

[VANILLA_GORILLA]

Originally Posted by slim

Did this start recently? If so have you replaced or changed something in the drive train (including wheels or tires).


Slim

Didn't seem like this problem arose until after I got the car back from a tranny fluid drain and refill but that doesn't seem like it would cause the problem.

[slim]

Nothing minor like tire rotation?

[VANILLA_GORILLA]

Originally Posted by slim

Nothing minor like tire rotation?

The old wheels have been on and off the car several times with no regard as to what order they went back on. However I just got new wheels and tires and the vibration is still there.

There's also a good clunk when I put the car in reverse from park if that matters.

[ToneMT]

U-Joints is my guess...Easy to do in your garage....

[VANILLA_GORILLA]

Originally Posted by bartl

Absolutely.

How to Change the Universal Joint in a Mustang | eHow.com

Looks like it's meant for a newer model, but basically the same.

I don't have a bench vice yet. What size should I get to do this job?

[ToneMT]

If you dont have a press/vise - remove the drivetrain and bring it to a local garage - much cheaper for them to stick on the correct U-Joint and you do the labor...