I recently picked up a rusty 94 Ram 2500 HD 4X4 gasser. I want to change the Differential fluid in both axles.

What brand fluid and friction additve do you guys recommend.

Use a gasket or sealer?

Thanks,

I would use sealant, name brand synthetic 75-90 front and 75-140 rear. Two bottles of ford ls additive.

Thanks!!

Why Ford additive?

Black RTV is commonly used in place of the gasket on rears. Your choice. If you use the gasket + RTV do not torque the bolts until the RTV is set up.. a couple of hours. Otherwise the gasket may split and squeeze out. Either way, clean well first (razor or putty knife + lacquer thinner or brakeclean).

For the lube... with general use I believe any 80W90 lube will work fine. If the rear is limited slip, a tube of additive is needed. Two tubes? Maybe for a big PU rear but suggest one tube first and add another if it chatters.

If you are towing hard, heavy and fast, 75W140 synthetic will provide more protection for high temp situations.

I am gonna use black rtv w/no gasket.

Thanks guys.

Use the Permatex grey sealant RTV...it's for use with gear lube.

Use mopar axle sealant orange or gray. No set up time required just put it on and bolt it up. For years the black was ATF sealant for the cars. Although they recently change so read the tube.