gonna change fluids all round, any thoughts on running synthetic in the diffs? 98' Cherokee, 4.0l autotrans. engine oil is going to be synthetic. i am not towing or working this Jeep hard at all. need your thoughts, opinions. thanks. Stumper

 

Full syn usually helps pro-long the life of components. How many miles your engine have? IF you have not previously used full syn in your engine I would recommend running a blend first. Sometimes with higher mileage engines they start to leak with the syn vs dino oil. Just a thought.

 

ok...107,231kms... real clean underneath, also read that using syn in the diffs can inprove fuel economy. it's -35C here tonight and dropping fast, suppose to be -48C with the wind, so the easier the fluid moves, the better, less resistance and more important, getting lube to those very important moving parts. have run syn in engines for awhile now, and no problems/leaks. just gotta keep an eye on everything. Thanks, Stumper.

 

i run valvo full syn 75w-140 in both diffs.

 

Scientific research says that synthetic oils are better than "dino juice". If you can afford to run the stuff and change it as often as required. I say go for it. It's, personally, out of my price range.

 

I'm lucky enough to get mine for free, but even if i didnt, i wouldnt put crap in my axles after all the money ive invested into them.

 

Well, after the new gears, carriers, bearings and lockers I bought and installed MYSELF...I wouldn't put crap in my diffs, either. The Valvoline gear oil I bought at the local parts store for a decent price I think is doing the job just fine......of course there are a lot of guys in racing world who rely pretty confidently on Valvoline products as well......Just had both diffs apart a couple of weeks ago to install the lockers. I'll be darned if those gear sets didn't still look brand new after being in there 2 years of daily driving to work, 3 trips to Ca. and back to Wa. and countless 4wheeling trips.

 

I run Royal Purple full syn in both of my Jeeps.

 

I run valvoline brand myself in my diffs. I also use valvoline for tranny fluid, motor oil and such. Have always used it and had realy good luck with it. As for synthetic well in the dffs I run a blend same for the tranny, engin get's dino oil.

 

I personally use Richmond 75w-140, but I do use Mobil-1 synthetic at the shops for the 9"-ers and the T-101A's.

 

Gonna run synthetic in both diffs, 75w90, got a brand name, Mobil. And for the price, it's not like I'm changing it every other week, I can afford a little extra. Thanks, Stumper

 

I changed mine with Royal Purple also.
75-90 in the front, 75-140 in the rear.

Shop manual sez to run 75-140 syn if you tow a trailer.

I just have a small 4x8 that hauls a couple of dirtbikes, but it seems good to run heavier stuff in the rear anyways.

Besides i lucked out on the 75-140.
A local distributer was clearing out his RP line. Got it for $5 a quart!

 

Well just to let you in on a secret...
Unless you have a big oil co. sponsor... everyone in NASCAR runs Mobil 1 synthetic in their rears. And that's a Ford 9" with a Detroit getting beaten on for 500 miles.

 

Axles and transfer cases aren't really picky about which fluid. Synthetics will work fine. I've used them in my axles before but switched back to ordinary oil after seeing how much that stuff costs. I used to change my gear oil once or twice a month with all that mudding i did. It's adds up.

Is there any actual proof that synthetic yields better results than traditional oil? I've read alot on it but never seen a test that proves it. Like two engines running side by side at the same speed until one blows or something like that.

 

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