Running Syn gear oil in your diffs

I have a ton of 75w-140 fully synthetic from amsoil. Anyone run something this heavy in your diffs,,, I have factory axles in my 55.

 

This is a big debate to some...but the last time I ran synthetic in my diffs (75W90 Valvaline Synthetic) everything was leaking...changed out with conventional, no problems. Maybe it's different with something heavier??

 

Is 80w-90 conventional gear oil good for the diff? How about a T14 trans? I don't mean to hijack his thread and my question deals with gear oil so it relates to his question. I searched and couldn't find much info and didn't feel I needed to make a new thread since this one was already here, so please don't flame me. thanks

 

I would think it would be too much for your colder climate.

as to the other question posted:
80-90 is fine for the diffs, trans, t/case.

 

The 55' wont be driven much in the colder months... this was more a curiosity thing I guess, I have a bunch of it that I have left from guy that ordered from me but never picked up, and I am gonna change the fluids again this week so I was thinking about putting it in the diffs first then maybe the Tranny/tc and see if it made any difference at all

 

free oil = good oil
and I misread the post
with the viscosity range it has, you should be fine.

 

Thanks Jim, gonna give it a try and will post with results good or bad

 

Run synthetic in both diffs, trans, and TC.

 

I have also run syn, but it has always been 80/90 or so, never used the 75-140 stuff. What do you run?

 

The Novak website says it's better to run a non-synthetic in the trans.

http://www.novak-adapt.com/knowledge/t14.htm

 

i run 90-140 castrol syngear in all apps due to cost =FREE!! runnin it in my 58cj5 for almost 2 years no prob itdoes not leak anymore than conv. i live in PA it gets pretty cold and i sub-contract with the old plow w/out probs.

 

80w-90 amsoil

 

They state it is not worth the expense.

The question I have is Novak's site recommends a GL5 oil. Doesn't the T14 have brass syncros? If so you should not run a GL5 oil. I have always thought the GL4 synthetic oil was the best spec to run for brass (or yellow metal) syncro transmissions. ??

 

run 85w90 synth in the truck in both diffs.

 

You should be fine running that in your jeep.

I would run synth in mine if I drove alot, but when I got offroading, I encounter alot of mud and water, so I change it often. Because of that, I dont run synth for expense reasons.


As for the trans issue. I've run GL5 in my T-15, and I hated it. It really did effect the syncros to the point that it was becoming very difficult to pull off smooth shifts. I switched to BG syncro shift, and now its smooth as glass. I've also run GL4 gear oil with success.

 

If a GL5 (synthetic or conventional) has MT-1 rating it should not harm or corrode brass inside the transmission and transfer. The better GL5 has the MT-1 rateing on the label. The cheap wallyworld GL5 is not MT-1 rated.
Novak also suggessts MT-1 capable lube.

As for 140W, wouldn't the increased drag cause more heat and more wear?



Tom

 

The stuff I ran was MT-1 rated.