After I got done my lift I drove it for a day with stock tires, but not over 45-50mph. Now with alignment and 31" mudders it is really noisy(like mudders). The rear tires are cupped pretty bad and make a lot more noise from 50-60mph. I'm pretty sure it is just the tires, but if I had a driveline vibration, at what speeds would it vibrate? I am going to do the trans case drop if neccesary, but I am pretty sure the bolts are going to snap. My rear lift is stock springs with a 2" block and 2" shackles.

I'm fairly sure it is the tires also.. Put the stock tires back on there and see if you have problems.. If it is the driveline the problem will remain..
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

The mud terrains were put on my stock rims, so I have no other tires. I am going to try rotating them and see if the problem changes to the front. The tires make noise at all speeds, but is worse from 50-60. Then it seems to smooth out. Searching the web a lot of people say vibrations from 50-60 is almost always tires. Anybody who has had a driveline vibration, at what speeds did it occur?

If there is cupping on the tires, you will have vibration and noise.

Mudders are noisy, period....

Before you rotate the tires, take note of the steering. If the front tires are smooth (no cupping) there should be no vibration in the front end.

Putting the cupped tires on the front should give you a slight vibration.

While you have an alignment, you have checked the front end. Now, has the rear end been checked for correct alignment??? ie, springs centered and square with the front...

After all, you did re-align the rear with the lift....

High probability it is the tires...

Since it only vibrates at 50-60 mph, it is most likely the tires, either the capped aspect of the tires, or their balance. As previously posted, swapping front to rear is the best way to determine that, as long as the front tires are not cupped, and you currently have no vibrations up front.

If it were driveline vibrations, you'd expect to feel the vibration starting as low as 10-20 mph and gradually getting more violent as speed progressed from there.

Also, with a 2" spring lift and 2" shackles, it's very unlikely that the driveshaft angle has increased with 31" tires enough to cause driveline vibration.

Thanks for the replies. That's the answer I was looking for. Everything on the web about driveline vibration never describes the speeds it starts at. The tires had been sitting for 3 years on a f-150 before I put them on the cherokee. The vibration seems less now than it did when I first put them on. Now they just seem like loud mud terrains. Still not as bad as my unbalanced 33" super swampers I had on my s-10.

Then, they will also be out of round -- ie. They will have a flat spot where they have been in contact with the ground.