98GTstang

What kind of differential lube do you guys recommend with ford 4.10 gears? What weight..ect. Thanks for the input.

lizzyfan

http://www.americanmuscle.com/royal-...-gear-oil.html

Soldier GT

+1 on the Royal Purple. If you're gonna spend that much money go with the best. Go to your local I forgot what weight I put in my diffs but you can go to your local Oreiley's OR Autozone and they will tell you exactly what weight you need.

WhiteFoxGT

I've always used Ford 75-140, and a bottle of friction modifier. Royal purple I hear is good stuff, however I have never used it

Soldier GT

Oh yeah forgot about the friction modifier not a must but something that would reall make a new gear install a success.

Davojan59

the friction modifier IS a must if u have posi...which all gts do

Soldier GT

Well I must have gotten lucky (which I'm sure I did). When I had 373's I didn't add friction modifier and had no issues. That's some good info man.

mustangman02232

75W90 dino (usually run valvoline as what the local store has)

disturbdgt

now if you use royal purple, do you have to get any friction modifier? because it says that no additives are needed.

Soldier GT

I guess you could be right. When I installed the 373's the mechanic didn't ask for the friction modifier. When I installed the 410s (with a different mechanic he wouldn't install them unless I bought the friction modifier). I bought Royal Purple on both installs and with or without the friction modifier haven't had any issues.....