I installed a Moser 12 bolt in my wagon last summer and probably put about 1500K miles on it since. It has the Detroit Truetrac locker in it and 3.33 gears. It has been great so far with minimal gear noise, but since I started taking the car out again after a winter's sleep, I noticed a whine when I decelerate. It seems to be getting louder and it's almost a moaning sound; louder at highway speeds and when it's warmed up. It stops when I step on the gas. What should I be looking for here? My first step is to check the back U joint this morning, because that's the easiest. Any other places to look or your theory on the cause would be helpful. I would hate to have to pull this thing out.

A bad u-joint will make a squeeking noise when first starting to go bad from lack of lube & then when the rollers are gone it will clunk when the load on it changes. I think your problem is internal. Improper setup on the gear pattern, backlash wrong, or a bearing going out. Have you checked the lube?
Mike

Haven't checked the lube but I filled it last year when I installed it, checked it a week later after break-in and haven't seen a puddle or even a drop from it since. I checked the u joints today and they are fine; pulled the wheels to look for leaks around the seals and there are no leaks.

Mike is right. there is a problem with the ring/pinion contact. Could be anything from a bad bearing to improper backlash setup. You should have it checked soon before you do any damage to the ring or pinion gear. P.S. First check the pinion bolt to make sure its not coming loose.

One other thing that I noticed is that the locker is making more noise than usual also. It is a very loud clicking almost sounds like a lugnut in the wheel cover and it only happens when decelerating.

I was able to check the fluid today and found it to be about a quart and a half low. Can't understand where it went, there is no oil residue anywhere, maybe when I filled it originally it didn't have time to redistribute before I checked it again? Things have quieted down a bit, I only had time for a short ride and I hope I didn't do any damage....Your thoughts would be welcome and thanks.

With it being that low on lube I would suspect damage. If it was mine i would pull it & look, especially with that noise you describe.
Mike

I am going to drain it and open it up this weekend. What should I be looking for in the way of damage? Any recommendations on gear lube? I drove it a few times this week already and things have quieted down quite a bit.

I took the cover off and the oil was perfectly clean and clear with no burnt smell. The last bit of it had a very fine silvery powder in it and the powder coated the bottom of the housing and the lower part of the cover. I'm thinking that powder is from the break in period? The gears and visible surfaces look clean with no blueing or chips. How does it sound to you folks?

I would take it all the way apart & inspect the bearings, both carrier & pinion. The original noise you heard sounds like the same thing my 79 Trans Am made when a pinion bearing failed.
Mike

Usually axle whine on decell is usually related to improper pinion depth and/or backlash.Make sure you are within spec's.