You have Vari Loks front and rear on a Quadra Drive, use the 75W 140 and make it synthetic. Use 4 oz of friction modifier in each axle.

https://www.morris4x4center.com/knowledge-center/jeep-wj-capacities-and-type/

I included this for the capacities. It does not mention the front Vari Lok but I can assure you a Quadra Drive has one and it also requires friction modifier. It says the 75W 140 is for towing, I just happen to use it all the time, you can use either grade in both axles, just make sure you use the friction modifier. The transfer case uses special fluid, some publications still use the old spec of ATF4, do not use that. You need Mopar MS-10216, part number 5016796AC.

 

You have Vari Loks front and rear on a Quadra Drive, use the 75W 140 and make it synthetic. Use 4 oz of friction modifier in each axle.

https://www.morris4x4center.com/knowledge-center/jeep-wj-capacities-and-type/

I included this for the capacities. It does not mention the front Vari Lok but I can assure you a Quadra Drive has one and it also requires friction modifier. It says the 75W 140 is for towing, I just happen to use it all the time, you can use either grade in both axles, just make sure you use the friction modifier. The transfer case uses special fluid, some publications still use the old spec of ATF4, do not use that. You need Mopar MS-10216, part number 5016796AC.

What he said. Qualification-it's possible that a PO replaced the front axle and didn't replace it with a Vari Lock. Ask me how I know.

 

I would physically check the behavior of the front differential.

Ff you want to check if your jeep has vari_loc in the front diff, lift front wheels and spin one tire by hand for a few revolutions. With an open diff the other wheel will turn into the opposite direction. When it has a Vari-Loc, it will start turning opposite direction, but after a short time, both wheels will turn in the same direction (as soon as the Vari-Loc is locked). If the tires stay rotating opposite directions the whole time then you have an open differential. You don’t need the FM in an open differential, but it won’t hurt anything if you put it in. As you pointed out, FM is needed for a Vari-lock differential.
IIRC, If your jeep has Quadra Drive (labeled near the shifter), it has the Vari-Loc in both axles.

 

You should have VariLok in both axles. The noise you mentioned on tight turns does indicate that a lubricant change is needed. Use the 75-140 synthetic and add Mopar friction modifer to each. It will take driving it some to get the new lube worked into the clutch plates (go around a bunch of corners both directions) and then your noise should go away.

 

Change the transfer case fluid as well. After servicing both my Vari Loks I still had a groan which I noticed went away with the front driveshaft removed. Changing the t/case fluid solved that problem.

 

Wow, i was not expecting so many quick responses, you guys are awesome!

I crawled under the jeep after work today and found that both Diffs have stamps on them that i didn't see before due to some surface rust. After some scrubbing, this is what I found:
Front Diff Stamp: 75W140 SYN 38 0Z FM 2 OZ
Rear Diff Stamp: 75W-140 SYN 72 OZ + FM 4 OZ

That being said, I will follow this direction for both type and quantity of oil and friction modifier. It was strange though that one stamp was an aluminum tag tacked onto the differential while the other was a dotted stamp directly into the differential steel. Not sure if there is any significance there, maybe one has been replaced.

Looks like I've got a lot to learn about these Jeeps, so I'm sure I'll be here regularly. So far I love it. Thanks again for all the help!

 

Wow, i was not expecting so many quick responses, you guys are awesome!

I crawled under the jeep after work today and found that both Diffs have stamps on them that i didn't see before due to some surface rust. After some scrubbing, this is what I found:
Front Diff Stamp: 75W140 SYN 38 0Z FM 2 OZ
Rear Diff Stamp: 75W-140 SYN 72 OZ + FM 4 OZ

That being said, I will follow this direction for both type and quantity of oil and friction modifier. It was strange though that one stamp was an aluminum tag tacked onto the differential while the other was a dotted stamp directly into the differential steel. Not sure if there is any significance there, maybe one has been replaced.

Looks like I've got a lot to learn about these Jeeps, so I'm sure I'll be here regularly. So far I love it. Thanks again for all the help!

I am sure it will keep you very entertained - either wrenching or planning your next wrenching adventure.
Am curious, where/how did you find one with 80K miles?

 

@ReeseLan - Congrats on snagging such a crazy low mileage WJ! Keep up on the maintenance intervals and it'll last a long while. I would suggest perusing the maintenance info here: https://wjbible.com/service/maintenance_wj.html .

For the differentials, I personally use Redline 75w-140 which already has friction modifiers blended in. (https://www.amazon.com/Red-Line-57915-75W140-GL-5/). Zero issues over close to 100k miles I've been using it.

I'd also suggest Lube Locker gaskets. IMO they're worth the $$$.

https://www.amazon.com/LUBE-LOCKER-LLR-D030-Lubelocker/

https://www.amazon.com/LUBE-LOCKER-Lube-Locker-LLR-D44HD/

 

Thanks for the tip, my main concern for doing this myself was the time available. I think I'll spend $40 to save a couple hours of dry time on the gasket calk. THe links above didn't work for me, but for anyone else, i found the products below on LubeLocker's website:

Dana 44 (rear): Dana 44- LLR-D044
Dana 30 (front): Dana 30- LLR-D030

Thanks again for all the feedback. Aside from building stress about the apparent dropped valve seat issue, I think I'm in good shape...

 

+1 on the LubeLocker gaskets. Reusable, and they don’t leak. Don’t waste time cleaning off paper gaskets or RTV. Every diff I open goes back together with one.

And use a torque wrench.

 

@ReeseLan - Apologies if the links didn't work. With Amazon I try to snip all the gogglegook they append to their share links and I guess I clipped too much.

Pricing for the Lube Locker gaskets is best on Amazon with their Prime shipping. If you're buying other things to bring the total $ up I've found Summit is a good source for them. Summit also has the CRFE gasket that will fit the 45/545RFE transmission, which I'd recommend along with the Dorman 265-817 transmission pan since it has a drain plug.

@GmanWJ pointed out that the typical maintenance interval for the differentials is 12k miles. That's going off the "B" service interval in the link I provided from the former WJJeeps webpage. 12k is recommended but that's not to say you've got to hit that mileage dead on every time. I'm pretty anal retentive with fluid changes due to the amount of mileage I put on monthly, but I'll allow for a 10%-15% overage on mileage for fluid changes.

If you want to make diff fluid changes quick & easy, invest some time on the first time you do the diffs. Drain the fluid, pull the covers, clean the mating surfaces on the diff & covers, eyeball the differential for any obvious damage (chipped teeth) or metal shavings in there, then clean it out really good with shop towels to get all the old fluid out.

Replace the covers using the Lube Locker gaskets, and I'd suggest using a torque wrench as @BDW pointed out. Lube Locker has previously suggested doing 2 rounds of tightening, 15ft/lbs the first time and 35ft/lbs the second time around. Buuuuuttt..... I've read several threads on other forums about people following that guidance and breaking (or stripping) diff cover bolts. With the D44HD in the back on our WJs being aluminum, there's a higher than average chance of stripping a bolt if you're just going by feel. I've got one bolt Helicoiled on mine from the previous owner apparently doing exactly that. I aim for 25ft/lbs on both sets of diff cover bolts.

For future fluid changes, the quickest way I've found is to loosen the very top cover bolt 1/2 way, then pull all the other bolts. The single bolt at the top will let the cover hang while you use a flat screwdriver to crack the gasket seal and let the fluid drain out the bottom into a pan. If you want to inspect the diff after it's drained, pull the top bolt and the cover. Otherwise, if you're just wanting to do a quick fluid change just wipe the bottom of the cover & gasket where any fluid has gotten on mating surfaces and reinstall the cover bolts. Refill and boom you're done.

There are other things you can do to simplify & speed up fluid changes.

Swap the OEM transmission pan for the Dorman that I mentioned above, the drain plug will make for a quicker & cleaner fluid change. The Lube Locker gasket will speed things up since it can be reused rather than screwing with paper/cork gaskets or RTV.

For oil changes, I've installed a Femco no-spill oil plug. It's worth the $45 I spent on it, trust me.
https://www.amazon.com/Femco-Compact-drain-7910155-M14x1-5-SB-T12/dp/B01N30AXCC

The transfer case is going to make a mess no matter what you do. I'm debating on one of those Femco plugs for it as well, but probably in a few months when I do my next fluid change on it.

When you do the transfer case, pull the fill plug first to make sure it wasn't overtightened or seized. The last thing you want is to drain the transfer case then find you can't get the fill plug out. Typically I'll wrap both the fill & drain plug with white PTFE pipe tape before I put them back in, and also don't overtighten either.