Rear end grinding noise

So I'm hearing this noise coming from the rear-end when I go around turns. So I got to thinking, and I don't think the place that installed the rear put the limited-slip additive in it. Could this be the problem? I hope so.

Thing is, since the rear's only a week and a half old or so, can I just put in the fluid? Or do I have to drain the oil out of the rear and put the additive in FIRST, then fill it back up w/ oil? Also what size allen wrench do I need to take out the plug for the differential? Or is there an easier way to take the plug out?

I hope they didn't forget, b/c that could have fried the bearings in your brand new rear. I would drain it and use the GM additive and see if it goes away, ASAP, like tommorow morning.

Don't panic. The GM posi additive has nothing to do with lubricating the bearings. It is a friction modifier to use with clutch style positractions.

Did your 12 bolt come with an Eaton HD posi like most of them do?
If so then don't even worry about the additive and do NOT use synthetic gear lube. The Eatons use a Kevlar clutch facing that doesn't like synth and does not require the friction modifier. If the noise bothers you then by all means you can add the modifier. But keep in mind that the friction modifier makes the grease more slippery. So that means you loose a tiny bit of posi action.

Now if it has some other brand of posi in it that requires the modifier then drain an appropriate amount of lube out and replace it with the GM friction modifier run it a little while making some turns and it will quiet right down.

ya it's the eaton posi. every install guide i've ever read on the moser though says in capital letters to be sure to remember the limited slip additive though :confused: hmm

FYI: I just called Moser and the guy said it's normal for the Eaton posi to make a chattering noise, but you still definitely need the additive, otherwise the chattering will be worse and the clutches will wear out prematurely.

:)

Moser doesn't make the posi Eaton does.
But Eaton is hard to talk to.
The guys that we talked to at DTS both said without any hesitation that the Heavy Duty Eaton with the Kevlar clutches does not need the additive.
If you personally feel safer having it in there. Do it.
But I know that there's 2 of us that ran ours hard all last year without with no ill effects. I run somewheres in the nieghborhood of 100 passes per year on slicks. We'll see in a couple more years how it's doing then.

Ya I know Eaton makes it, I just figured I'd ask Moser. Oh well, I didn't put the additive in it. I couldn't get that damn fill plug out to save my life. I put all my strength into it and it didn't budge. :rolleyes:

Originally posted by GrdLockV6
Ya I know Eaton makes it, I just figured I'd ask Moser. Oh well, I didn't put the additive in it. I couldn't get that damn fill plug out to save my life. I put all my strength into it and it didn't budge. :rolleyes:

You don't have to use the fill plug in the cover. Use the fill/check plug on the passengers side of the pig. It's just above the web. Just stick a 3/8" extension bar into it with a ratchet. It's a square drive plug.