Here goes... about 10,000 miles ago I did my brakes. When I did them I realized that my left rear caliper was hanging up a good bit and the break pad was completely destroyed. So I changed the breaks on all 4 corners. THEN I also noticed that I had a leak from the rear pinion seal. So I changed that. I didn't take the whole diff apart... I just marked the pinion nut, counted the number of turns to get it off, changed the seal, put the nut back on with the correct number of turns and then torqued it pass the mark I made by ~1/16th of a turn.

Now after I did this, ~10,000 miles ago, I noticed a "humming" when I accelerated somewhere between 0 and ~15mph. It is a "rotational" hum... much like the sound of a brake pad hanging up on a rotor. Not a continuous hum, kinda like it would hum when the pad hit the high spots of the rotor. After 10-15mph the hum goes away and I never hear anything again. The sound has not gotten worse over the past 10,000 miles.

Now, I am not sure if the sound is just the caliper not opening smoothly after I get off the brakes, causing it to drag on the rotor until I reach 10-15mph and humming as the rotor goes around. OR if it is differential noise... likely pinion bearing or pinion pre-load.

I have tried to slightly hold the brakes as I accelerate from a stop and the noise goes away.

What do you guys think, brakes or diff making the noise? Any good tests I could do to figure it out?

Thanks guys!

 

Do you have factory LSD???

 

I am 99% sure I do.

 

Then I'd pop the pumpkin off and be looking for a broken "C-Clip". When is the last time you pulled the cover off to change the diff fluid (30k intervals)???

 

Never, I haven't put that many miles on it yet. When I did the pinion seal I sucked out all the old fluid and put new in.

How would a c-clip cause this? The axle is "walking" in and out?

 

Different "C" clip. The clip Hammer is referring to is one or more of the clips retaining the limited slip clutch pack. They are smaller than the axle retaining clips and are actually sort of "W" shaped. Although if one of those clips are your noise it won't look like a "W" shape when you find what's left if it.

 

LOL. Cool.
Also it is hard to remember if the noise started directly after I did the pinion seal. As I said I also new I had a problem with that rear caliper as well and I replaced them within a week of each other. Also, this noise MAY have been going on before I did the pinion seal I just never noticed it. Cuz as it goes AFTER you work on something like a differential, you become VERY attentive to new noises. lol.

 

Never suck the fluid out of a differential and bypass the opportunity to inspect it and get a good look at the ring/pinion/spiders and above all else, the LSD clutch pack retaining clips since they will fail at some point on EVERY AAM 9 1/4" rear axle...

 

Noted. Thank you.

So a broken LSD clip would cause the symptoms I described? If so I will pull the cover sometime this week... when its not 20 degrees outside, lol. I just got done replacing the water pump this past week... it never ends.

 

I am looking at the factory service manual right now. There is only 2 pages on the LSD, and not very detailed(unless I am missing something). Is there a write up, or pictures of the c-clip so I can see what I should be looking for.

Thanks