Hey guys !!! I want to dump the old fluid out from my tranny( 4 speed) and rear end (Dana) ...and put some fresh stuff in.... what is recommend ?? Thanks !!!!

Diff is GL-5
Tranny is GL-4
don't thing that the GL-5 is an upgrade to 4, it has different additives in it for the syncro's vs the limited slip friction modifier. tim

GL-4 for the transmission, it is an antiwear antifoam oil with rust and oxidation inhibitors.

GL-5 is the same as GL-4 EXCEPT it has Extreme Pressure additives. These additives are active on the metal surfaces, forming an oxide or similar layer which protects the surfaces should the oil film allow them to touch. They like to attack yellow metals like brass parts in synchros. They also make the synchros less effective so shifting is harder and sometimes noisier. The GL-5 designation has absolutely nothing to do with limited slip differentials.

The invention of the hypoid gear was the reason for the development of EP additives. Those gears in the rear end have sliding contact.

I like synthetics because they have a flatter viscosity curve which means they work better starting out from cold.

Passon has his own variety of transmission lube and as he is one of the two A-833 gurus on here I'd use his, or else whatever Brewer's is recommending.

For the differential I'd pick a good 75W-90 synthetic at Autozone or wherever.

R.

GL4 90 weight lube for the transmission as recommended may be to find. It can be ordered from Summit or even better is Redline MT90 synthetic fluid. I imagine the Passon lube is good but no personal experience.

For the rear end, synthetic can take the heat better but there may be an increased chance of leaks if the rear has been run with conventional. If the current lube is conventional, I'd suggest common 90 weight (or 80W90). If you plan extended hot high speed running, xxW-140. If it has a sure grip it also needs the SG additive.

Thanks guys !!!!