I think it's time I change my diff, tcase, and oil. My last oil change was done little over 6 months ago, and I unfortunately had to use JiffyLube, which used a small filter. For that I planned on going with Mobil 1 5w10 with matching filter, since the colder months are approaching. Now I've only had this Jeep for over a year, and honestly haven't replaced the diff, tranny, tcase fluid. Neglectful, I know. I hate it. For the front, I think I have an Aussie up front.. lol The previous owner said it has one, it has a diff guard, I feel like there's a locker then when I'm on the trails, but I can't compare it since it's my first Jeep.. Should I open up the diff before I go to the store to double check, or how would you recommend I check? If I do have an Aussie, 2 bottles of 85W-140 gear oil, right? For my rear 8.25, which is open, 75/90? And then for tcase Dex III? Should I do the trans too? Since I technically don't know the last time it was replaced? I know it's similar to the coolant system, so just don't flush? Or just a new filter?



Cheers and sorry for the lengthy post.

 

Mobil 1 75w-140 is Perfect for both front and rear diffs(High dollar, around $20 a bottle) and can be used for extendend miles(50,000) transfer case uses ATF DEX/Merc, I would recommend Mobil 1 or Castrol ATF.

 

Should I only use that 75w-140 if I have an Aussie, or is that if I don't?


Thanks

 

Engine oil: Mobil1 5W30 as you say is a good choice. If you can find the "High Mileage" stuff opt for that, it has the extra ZDDP that the 4.0 needs.
Oil filter: Mobil1 M1-301 is a larger size that will filter more gunk out. It's the same price as a regular filter, so you might as well extend your oil change interval since you run synthetic. If you want to save a few bucks try the WIX 51515/NAPA Gold 1515 (the two are the same unit)
Diffs: If you're offroading, a synthetic 75W140 would be a very good idea in both diffs. Your rear will be working hard too, even without a locker or limited slip.
Transmission: Automatic (AW4) takes D/M (meets Dexron III/Mercon specs), manual takes API GL-3 or API GL-4 oil. Do not fill an AX-15 with API GL-5 or 10W30 motor oil. If you can find Pennzoil Synchromesh, or anything labelled "synchromesh" that is brass safe, use it. If you wanna spend the dough pick up Redline MT-90
Transfer case: Dexron III/Mercon again

 

Thanks a lot for this! Very helpful! So for my auto trans, I should get something similar to this then? http://www.pepboys.com/product/details/8545657/

Also, where do I find out the sizes of the diffs, tcase, trans, to find out how much I should buy? And what type of trans filter do you recommend?

 

Yes that fluid should work just fine. Any transmission filter will work just fine.

You will need to pick up 2 quarts of fluid for each differential and tcase.

 

I'm going to pickup new oil/filter tomorrow and change it, then going to hold off on diff and tranny for another week or so. Only since I'm saving money towards the 6.5'' lift. I was wondering though.. is there a transmission additive I can run through my transmission? It's not leaking or anything, but maybe something to help clean it up that can be run through it for about a week or so?


Cheers

 

Such beasts do exist, I've seen Seafoam TransTune on the shelves but no idea if it's a clever idea in the AW4. Do you know how dirty your transmission is inside? Autos are famous for problems after flushes. The safest way to clean them out is the gentle drain and fill approach: drain whatever's in there now, fill with something cheap, and change after a week. If the fluid is really bad and you suspect it has never been replaced, you may want to reduce it to drain a pint, top off a pint, then keep doing that to gradually change the fluid. I'm not an auto owner but it makes sense that the shock of fresh detergents could blow something loose. I'd do something similar with an engine if the sludge wasn't too bad.

 

Ah, I see! Good to know! I'll approach the trans fluid differently then. I'll look into the gentle drain/fill approach. I check my dip again but I don't think it was red-ish at all.. And is a sealant never recommended? I used it last year in my oil and it helped me leak, now after my last change, it's back again. Then I avoided it when filling my coolant. I like the idea of using the cheap stuff for a week, then replacing it. Seems like the safest route.

 

Using it as a temp fix to get you back home is OK, but outside that most leak sealers are time bombs. The leaks most always come back, generally even worse and at the worst time possible.

 

Highly agreed. I wont run them.

 

Good to know! How should I go about fixing this oil leak? Obviously narrow it down to where it's coming out at, but then what?

Thanks

 

The leak could come from a few different places - valve cover, oil filter adapter, oil pan or RMS. Replace the gasket and dont overtorque it and you'll be good to go