Jeep: 97 Jeep TJ squeak coming from wheels, wheel bearings, differential changes

Question
I was reading thorough the threads and I think I may have found my answer, but I'll ask anyway.  I have a squeak/whine coming from (I think) my rear end.  Always happens in cold weather and goes up in pitch with an increase in speed.  Quiets down and stops when under braking.  Starts at speeds over 10 mph and up.  Is it my wheel bearings?

Answer
Craig,

Advising on noises over the net is difficult at best, but I have a few thoughts...

Does the noise oscillate at all (kinda like a siren), and if so, is it relative to wheel rotation? Is it possible that it's 3x times the rotation of the wheels? Is it just louder when cold, or only noisy when cold? Does it fade as it warms up?

If it's the same speed as the wheels, you might check the rear brake system -- they have been known to snap a spring or two (the shoe-to-shoe spring, to be specific). The wheel bearings are really more associated with growling than whining or squealing, but it's not out of the question. Applying the brakes shouldn't affect that, however.

If it sounds something like an annoyed bird (with oscillations 3x the wheel speed), it's possible one of the u-joints is noisy. They should be periodically checked anyways (during tire rotations or oil changes), and since there is no less than 5 (double on the prop shaft) -- that's plenty to squeal!

Chances are, if it's loudest on non-braking deceleration, the rear differential pinion bearing(s) are whining. They are inside the rear differential, suspending the pinion gear in the axle housing. If you check the fluid, look for a silvery appearance to the fluid, or even black like it was burnt. Normal gear lube should be thick like syrup, and somewhat similar looking, yet clearer, than motor oil. It should be a Dana 35, and the plug is on the rear service cover. Since the angle of the differential changes when braking, that could explain the change.

If it's more on acceleration, then try and pinpoint *where* the sound originates - there's not too much else that whines with that symptom. Barring that, have a friend ride with you , in order to put a second ear on it (especially if it's a mechanic friend!)

Good luck!