I have bought a 93YJ with 70,000 miles on the clock. The rear leaf springs are sagging and are shortly to be replaced.
I have found a really strange vibrating noise that is really loud around 40mph. As the speed of the vehicle inreases the tone gets louder.
It sounds similar to a worn wheel bearing, but we have changed them. Although the sound seems to come from the rear axle area its difficult to tell.

When bringing the vehicle to a halt the vibration is really bad like a vehicle with an overly agressive tire stud pattern on tarmac.

Has anybody had similar symptoms?

Can anyone offer a good way of being able to find the problem quickly, rather than spending time and money replacing parts that may not need it?
Sorry if my description is rather poor.

Almost sounds like a bad or unbalanced tire. Try swapping the tires front to back to see if your vibration changes from the rear to the front.

TWO JACK STANDS AND RUN IT IN PLACE..
Damn caps key!!
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

Check the joints on the rear propshaft. If they are greaseable then give them a couple of squirts of grease and check if the symptoms change. I have had a similar problem twice before and one was worn out U-joints and the other was a totaled draglink.