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Open diff or LSD?

103 views 7 replies 3 participants last post by  Don Fox  
#1 ·
Hello,

Today I set out to change the differential oil in my 1998 Dodge Durango (5.2L, 4x4 SLT, 12-bolt diff cover). I ran the VIN through a decoder to check if it had an LSD (limited slip differential). The result showed it should be a 3.55 ratio open diff, no LSD.

However, after pulling the cover, I noticed what looks like a clutch pack inside, which makes me think it does have LSD. The VIN decoder was also wrong about the ratio — the tags on the cover bolts say “0638” and “3.9,” which points to a 3.92 gear ratio instead.

The glovebox sticker doesn’t mention the differential at all (only transmission and paint info), so that’s no help either. I know I could lift the rear end and spin the wheels to check if they rotate in the same direction, but my Durango is lifted and I don’t have a jack tall enough to raise it where it’s currently parked.

Could anyone help me positively identify this differential? I’ve already bought two quarts of 80W-90 gear oil, but I’m not sure whether I also need a friction modifier.


Thanks in advance!

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#2 ·
TF:
From your pics, there is no clutch pack there. That is an open diff. Since you have 4 x 4, take a look at the front diff. There should be a white label with a bar code and the ratio next to it. 3.92 was the less common factory ratio, as around 33% of the Gen 1 and 2 Durangos had it.

Since you have the 9.25 and not the 8.25 rear end, your D is part time 4x4 correct?

Don
 
#4 ·
I'll agree that upon a 2nd look, it appears that there could be clutches behind those spider gears. One way to tell quickly. With both rear wheels up off the ground, try to rotate one wheel. If it won't move easily or at all, you have the Anti Spin as Dodge calls it. If the wheel turns, and the wheel on the other side goes the opposite way, the diff is open.

Don
 
#6 ·
ww.fm:
I do see that the non AS carrier has a sort of cone shape on the right end, whereas the AS carrier is more squared off.
Hopefully the OP will perform the simple test I outlined, and report back.

Don
 
#7 ·
Hi, thanks for all the replies. It turns out this is indeed an LSD differential, not an open one. I ended up adding a bottle of Mopar LSD friction modifier along with the gear oil.

At first, I planned to do the oil change the “easy way” by pumping the old oil out through the fill hole, but I’m glad I pulled the cover instead — otherwise I would never have discovered that it’s an LSD.
 
#8 ·
TF:
Did you perform the test I mentioned or learn another way? Anyway, you have your answer. I've not seen an LS differential like that, but as we say, you learn something new every day.

Don