Hey guys and gals, I don't have an owners manual (yet) and need to know the correct fluids to use in the differentials and transfer case. What does the manual recommend and/or what do you put in yours if there's something better?

Thanks!

gear oil in the diffs, and ATF in the auto tranny and transfer case.

just a good dexron 3 etc ATF.

Yes as Noob says make sure to use Dextron for tranny and Transfercase. As to the diffs I use Valvoline or more recently Royal Purple 80/90 gear oil.

Cool, I've got an extra quart of Dex/Merc sitting around that I'll use in the transfer case. Lucas has their own brand of gear oil, so I bought some of that today for the diffs. I got 80W90 for the front and 85W140 for the rear...probably overkill for the rear, but I will be doing some mild towing and thought what the heck.

I did a search here and found a reference to adding friction modifier to the diffs I think only if you have LSDs. How do I know what I have?

There should be a tag on the diff itself. Also there was a sticker inside the glovebox on MOST limited slip equipped models.

But the other two ways are either open up the differential and the two carriers look different. The limited slip model has a more squared off shape and the open carrier is rounder, and has alot more open space.

Or jack up the rear wheels and leave the jeep in neutral. Turn one tire. If the opposite tire spins the same direction, you have a limited slip.



On the left is an open carrier, on the right is a LSD carrier.

Thanks whowey! If no sticker in the glove box, I'll jack up the rear to perform that test. Will avoid taking the cover off to look if I can help it

No sticker in glove box to indicate LSD, so jacked up rear. One wheel spins forward, the other one backwards, so no LSD. Tag on the rear diff with a "35", so that's Dana 35 I guess. Front and rear fluid looked really good, so it must have been changed. Topped off the rear with 85W140 since it was 1/2 pint low. Too bad there's no drain plug on either one or I would have drained since I had the fluid ready.

Only way to drain em is to pull the covers off or pump it out. Drain plugs would be cool though.

Wonder if we could get RuffStuff to incorporate a drain plug in future covers? The reason they are not on stock is that even w/o a plug you have fluid lubeing the gears and if the bottom drain plug vibrated out you would lose that insurance that the single plug affords you.

What about in a manual tranny?

Which tranny do you have True? I will look it up in my FSM for you.

The AX-5/15 takes a 80w-90 GL-3. That is not what the FSM is going to spec, but that is a known mistake. Sulfur in GL-5 lubes will attack the yellow metal portions of your transmission.

Thanks whowey I had read that somewhere and glad you explained it. The TJ has a similar discrepancy with the NV3550 too as I recall.

I knew there was something with the brass synchros, just couldn't remember. But ATF in the 231?

Yes.. that is what New Process recommends.