i JUST CHANGED MY DIFFERNTIAL LUBE WITH REDLINE 80-175 SHOCK PROOF LUBE AND ALSO ADDED TH FORD FRICTION MODIFIER. wILL THIS CAUSE ANY PROBLEMS. fORD CALLS FOR 75-175 LUBE.

 

I think it's 75w140 for the rear axle. (75w90 for the front on a 4x4) I know, because I just bought some Amsoil gear lube for mine today. Also got the Ford Friction Modifyer for the LS.

The numbers are the same as motor oil. The first one is the weight when it's cold, and the second when it's hot.

I don't know the effects of running too thick of an oil in the diff? Always used what was spec'd for one. It 'could' cause more wear because the oil won't get into all the nooks and crannies that the lighter oil would......????

I guess if you live in Arizona, it's probably not that big of a deal. If you live in the North, then I'd say you might have a problem when the oil is cold...... Again, not an expert, just telling you what I think....

 

I made a error I used 80-140 oil ford calls for 75-140 like you said. Thanks for your advice