Ford 9" question
 

Hey guys,
I have 9" in my car, it's a 31 spline 3:55 rear end. It had a spool in it but I bought a trac-loc kit from Yukon with new bearings and everything. I pulled the 3rd member and took it to a shop that does a lot of heavy duty rear end stuff for off road trucks. They put the trac-loc and bearings in and set the diff up for me.
After I got the 3rd member back in the car, I took it out for a drive and it has this loud whining noise like a gear drive would make. It makes this sound mainly under acceleration, when you back off the throttle it quiets down. It also get louder the faster I go, really bad around 50 mph.
I took the whole car back to shop where I had the work done and they pulled it apart for me. They re-set the tolerances and put it back together. Same problem still exsists. I did not put new gears in, just bearings and the posi unit.
I had been driving the car with the spool in it for a couple years with no noises at all.
To me it sounds like the noise is coming from tranny area, but it's awfully coincidental that it started after the rear end work. Maybe the noise is traveling and making it sound like it's coming from somewher up front? It has a M-21 that does not have many miles on and the pilot bearing is brand new. The motor and trans have only about 150 miles on them.
Maybe I have the wrong diff fluid in it? I think the shop put 75-90 synthetic in.
I have different people telling me different things, like it's a throw out bearing, a pilot bearing, a bearing in the tranny or a synchro in the trans.
I don't know where it's coming from but the car goes in for paint tomorrow so I guess I'll figure it out later. I was hoping to have the paint done and be finished with the car and just drive it, but it looks like I'll be tearing something apart after I get it back :(

No noise right before the rear diff work, but making noise right after... that's a bit of a no brainer as to what's whining. Did they find any setting being off when they looked again? You didn't mention anywhere if they rechecked the pinion gear depth. And while they were in there, new pinion bearings would have been a good idea too. I'm betting pinion depth being off (bad gear mesh) is likely to be the cause of your whine. Ask if they checked the pinion depth, although they certainly should have.

They re-set the mesh and said everything else looked good. Do you think a pinion bearing would howl while only under load? I'm not sure they changed the pinion bearing since I don't know if the kit came with one.
I will give them a call and ask a those questions about the pinion depth and bearing.
Thanks 69

My friend had a Detroit Locker and it made a whining noise and a loud clicking noise when you went around curves and I know that rear was setup right, so it may just be that this carrier makes noise.

You got to remember, when you hear noises coming from under the car, it is sometimes very hard to determine where it's coming from, but it is funny, that since the new carrier got installed, your now hearing noises.

But like Camaro 69 stated it's better to be safe and make a few calls first.
I'd call Yukon as well and talk to them, but you may end up finding out that the carrier is going to be noisy.

Maybe too much pinion bearing preload? And bruce69 the rear end you are talking about is a fully locked differential right? that would cause noise around corners because there is essential no differential action occuring. The left and right tire will try to turn at different speeds but a locked differential prevents that and that loads the rear end causing it to make noise.

The clicking noise when turning is normal for almost every locker I've ever heard. Mine makes some clicking around corners, but not very loud.

The noise, from what I understand came from clutches releasing when you went around corners, but I can still remember hearing a whining noise on straight runs.
Maybe I was hearing "bells" ringing in my ears but for sure, when you went around corners, it was like a popping noise.

my tru trac is sorta the same. took it back and had it checked, i was told it was the aftermarket gears whinin

If you have a clutch type LSD, it shouldn't make noise in a turn. If it does, that means the clutches are sticking, which is a sign of it needing an oil transfusion, with the additive.