TJ Dana 44 Trac-Loc LSD without friction modifier? -
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post #1 of 5 Old 06-01-2010, 06:22 PM Thread Starter
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TJ Dana 44 Trac-Loc LSD without friction modifier?

I have a 98 TJ with a D44 rearend with the factory-installed Trac-Lok limited slip differential.

I recently (few months ago) had a seal and bearing replaced by a local shop (I just don't have the time to do major jobs myself nowadays), and the guy assured me he'd topped off the fluid.

My rear axle now seems to be making some noise, particularly when taking turns at low speed (5mph or thereabouts). It's like a rumbling sound and it feels a little rough.

Either this just started, or, it's been happening for some time and I just hadn't noticed it; but in any case, I'm suspecting that the guy at the shop didn't add friction modifier when (/if) he topped off my diff.

I'm going to check it out this weekend and refill it with all new fluid. But, in the meantime... will running a LSD without the friction modifier damage the axle or the LSD in any way, or will performance/behavior be restored when I refill it and work the FM into the clutch packs?

I'm going to stop driving it (getting a ride to work from the wife) until I can refill it but the noise has gotten me worried about the health of my axle.

Last edited by GunmetalX; 06-01-2010 at 11:37 PM.
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post #2 of 5 Old 06-01-2010, 06:50 PM
Jerry Bransford
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99% of the proper GL-5 gear lubes come right from the factory with the proper friction modifier additive already added. So if you refill it with fresh GL-5 gear lube, don't add more friction modifier separately if the gear lube you buy says something like "Compatible with limited slip differentials" on the back label as it most likely will.

When you have a choice, buy American made.
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post #3 of 5 Old 06-01-2010, 11:20 PM Thread Starter
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Thanks Jerry. I've noticed that on the store-bought bottles before and wondered whether it was just printed there so owners of LSDs wouldn't be discouraged from buying it (and then still adding the FM). So, the last couple of times I changed the gear oil I still added the FM without being 100% sure whether it was necessary.

That said, do you think the rumbling/growling sound could be due to a lack of FM in the gear oil the shop used? Or could something else be going on?

I'm strongly inclined to pull the cover and check the condition of the teeth but it's hard to find the time to do all the work the right way (pulling cover, scraping away the old gasket, reinstalling, refilling, etc.) so I was hoping that a drain (using a pump) and refill with FM would just make it "go away" but maybe I just need to bite the bullet and keep it off the road until I can get to it. Unfortunately it's my daily driver so I'll need to bum rides to/from work from the wife for a while.

Last edited by GunmetalX; 06-02-2010 at 12:17 AM.
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post #4 of 5 Old 06-02-2010, 09:28 AM
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The noises you are describing are consistant with what you experience when lacking friction modifier.

For a quick fix, try adding 3 or 4 ounces of friction modifier.

Drive the Jeep for a few days, let the additive soak in and condition the clutches, and see if it goes away.

If the problem persists, you have further investigation to do.
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post #5 of 5 Old 06-11-2010, 08:29 PM Thread Starter
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So I pumped out the fluid, added the tube of modifier, and refilled.

Seems to have resolved the problem. Thanks everyone for the help.

Also, FWIW, on the question of whether typical lube already contains the modifier... I'm thinking it doesn't. My bottle of SuperTech (and by memory, other name-brands I've seen, but it's been a while since I looked) says something like "suitable for top-off and refill of standard differentials" and "suitable for top-off of limited slip differentials." So it seems to indicate that you still need the additive if you are doing a refill (or, I imagine, a partial but significant top-off).
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friction modifier , limited slip additive

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