Best Gear Lube for 1970 Formula 400 Firebird 4 speed and 12 bolt differential
 

Hey...I recently purchased a 1970 Formula 400 Firebird (numbers matching) and am new to PY Online. I'm planning to change the gear lube in the 4 speed trans and rear end and wanted to see if there's a recommended fluid to use? Thanks for any assistance.

https://forums.maxperformanceinc.com...89#post6154289

Murf

ETA, NAPA carriers Sta Lube products around hear. Amazon also.

Whatever gear oil you use, don't forget the GM brand posi additive or you'll get binding.

Also, pictures and details of your car are mandatory. :)

I contacted Valvoline a couple of years ago specifically asking what to use in Muncie transmissions from the 1960's, Here is what they recommend: https://www.valvoline.com/en/synchromesh-mtf/

And for the rear end, any quality GL-5 and I completely agree with the genuine GM limited slip additive if you have a Safe-T-Track differential. Notice I did not say Posi, it is a Pontiac after all, not a Chevy.

No synthetic for Posi's, Safe T Track or any other clutch type diffs.

On the transmission, synthetic is fine, but I like to add " MOTOR KOTE" This additive is amazing, and quiets many gearboxes.

After blowing up many a 12 bolt I finally switched to moroso climbing gear lube never broke one again. And I drag raced on these rears for years .

Back when I switched all the stock eliminator guys ran that lube.