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Thread: 12" AAM rear diff 'anti spin' Reply to Thread
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  Topic Review (Newest First)
05-23-2019 11:06 PM
esminbritt
Quote:
Originally Posted by Jhenderson View Post
Iíve got a months salary that says Iíve pulled apart more clutch type diffs than youíve ever seen. Many of them came to me because of complaints of chattering, sticking, or noisy rear ends. This comes from a lack of friction modifier, (for GM it was a type of fish oil) not a lack of lubrication. Not one of them had damaged clutch plates. After initial inspection the repair was to add the modifier, go to an empty parking lot and do tight circles in both directions under light throttle until the clutch packs freed up. Once again, no damage, just a poorly functioning limited slip.
Ok. So my pig has clutches. Since it is an AAM, would that make it a Tracrite PC?
05-23-2019 11:06 PM
Lins
Quote:
Originally Posted by esminbritt View Post
Quote:
Originally Posted by Lins View Post
Are we having brain farts here?
Yes. Yes we are
Ok just checking.
05-23-2019 11:04 PM
esminbritt
Quote:
Originally Posted by Lins View Post
Are we having brain farts here?
Yes. Yes we are
05-17-2019 10:45 PM
Jhenderson Iíve got a months salary that says Iíve pulled apart more clutch type diffs than youíve ever seen. Many of them came to me because of complaints of chattering, sticking, or noisy rear ends. This comes from a lack of friction modifier, (for GM it was a type of fish oil) not a lack of lubrication. Not one of them had damaged clutch plates. After initial inspection the repair was to add the modifier, go to an empty parking lot and do tight circles in both directions under light throttle until the clutch packs freed up. Once again, no damage, just a poorly functioning limited slip.
05-17-2019 04:22 PM
BTGreen You have a clutch type limited slip rear differential.

You do not have any helical/torsen/magic wizardry differential.

You need to use a friction modifier or approved lubricant or clutch damage will result.
05-17-2019 03:32 PM
Lins
Quote:
Originally Posted by esminbritt View Post
Apparently, it is a clutch type and does need the modifier.
Quote:
Originally Posted by esminbritt View Post
It definitely has limited skip. The question is which limited slip.
Are we having brain farts here?
05-17-2019 03:14 PM
Jimmy N.
Quote:
Originally Posted by Lins View Post
If the manual requires modifier it should be clutch pack, if it still doesnít require modifier then it should be torsen style.
We already know that it's not a helical gear type. That's obvious from the photos.
So if it is a clutch type, it may work fine without any friction modifier, and if not, then some could be added.
05-17-2019 03:01 PM
Lins If you really want to know pull the cover, the gasket is likely still the reusable type.
05-17-2019 02:58 PM
Lins
Quote:
Originally Posted by esminbritt View Post
Quote:
Originally Posted by Lins View Post
I'm not sure about the 12", but the AAM's on the previous years claimed no additive was necessary, but some people are getting chatter and said adding it helps. Also, on my '02 1500 it required additive but I still had to add extra additive to fluids that already contained it. Each diff has it's own personality apparently...

As for finding out what's in yours, jack up the axle and see if one wheel is free or not. Previous 3500s all had limited slip I believe.
It definitely has limited skip. The question is which limited slip.
If the manual requires modifier it should be clutch pack, if it still doesn’t require modifier then it should be torsen style.
05-17-2019 02:55 PM
esminbritt
Quote:
Originally Posted by Lins View Post
I'm not sure about the 12", but the AAM's on the previous years claimed no additive was necessary, but some people are getting chatter and said adding it helps. Also, on my '02 1500 it required additive but I still had to add extra additive to fluids that already contained it. Each diff has it's own personality apparently...

As for finding out what's in yours, jack up the axle and see if one wheel is free or not. Previous 3500s all had limited slip I believe.
It definitely has limited skip. The question is which limited slip.
05-17-2019 01:48 PM
Jhenderson Actually, my 2015 3500 calls for 75-85 . The reason for my post was in reply to concerns about Torson style diff operation with the modifier included. That being my limited slip works fine using it as well as my wife’s GTO which has clutches.
05-17-2019 01:36 PM
Jimmy N. I would suggest putting whatever 75W/140 in there that you like. Then, if it doesn't perform properly without it, add some friction modifier.

After all, there are people putting FM in open diffs and (real) lockers, and others that run clutch type diffs, which may or may not need it, without any friction modifier. And it still all seems to work fine for the most part.

Personally I wouldn't add a thing unless the diff was misbehaving, since it most likely will perform better without any additives.
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