*What to use IN front and rear diff.... I've heard different things, ATF, Gear Oil, etc.. So what do you run in an 8.25 and a dana 30?

 

I use 85w-140 gear oil. It's more heavy duty than the recommended 75w-90 for stock, but I have big tires

 

yea im changing it when I do my lift so I will too. 33's

 

Yes definitely gear oil. I run 75-140 as well. And synthetic or dino juice I'm sure both will be fine.

 

I use 80w90 in some heavy-duty worm gear (read: heavy shear) drives in our roll form plant. A Cherokee with big boots can't come close to the stresses involved there. I use the same in my diffs...guess its just preference. 140 seems a little too viscous for me, you're just creating more heat from friction.

 

This is what i'm using...



.......as per FSM.

 

If you Care about your Cherokee, I would recommend Mobil 1 75w-140 for both front and rear differentials, regardless if its the Dana 30 front High pinion with CAD, High pinion, Low pinion, they All do well with Mobil 1 75w-140. Rear Dana 44s, Dana 35 early(non-Clip) late Dana 35s, Chrylser 8 1/4s All do well with Mobil 1 75w-140 as well. Mobil 1 is EXPENSIVE though, but You Do get what You pay for. If you want to just get by fine with something more Affordable, then I would recommend SuperTech 80w-90 or 85w-140 gear oil. the very thick 85w-140 would be good for a tow vehicles rear diff, or both front and rear diffs if you live where its warm to hot temps all the time.

 

You will only be able to find 75w-140 gear oil in Synthetic form, by the way. 80w-140 is the thinnest/thickest combo you can find in Conventional gear oil.

 

And you just fill it till it starts to drip out the plug right?

 

Yes

 

yep.. i just did my rear diff last week.gonna do front this week if it will stay dry outside. dont know about trans though.mine is a 95 5 speed, i think its atf.

 

And remember, if your rear diff has the limited slip, you are supposed to add a bottle of the friction modifier in with the oil so the clutches can operate quickly.

And no for the trans its not ATF. You should be running GL-3 or GL-4 grade gear oil. This means that there is no sulfur in it, thus it will not be hard on your brass synchros. Regular gear oil is GL-5 and is not good for these transmissions. I use Redline MT-90 and thoroughly enjoy it.

 

where can you pick up the tranny gear oil?

 

pennzoil synchromesh....napa

 

Adding to this, most (all?) of the synthetic GL-5 gear lubes I looked at came included with the limited slip additive. Handy for differentials but really don't want that in your transmission.

GL-4 does have sulphur in it as part of the Extreme Pressure additive, however the spec is about half that of GL-5.

Castrol also makes a Synchromesh product. I had to settle for ACDelco Synchromesh stuff which seems to be thinner, nobody in town apparently sells decent fluid for me AX-15 .