306stang

I've got two bottles of 140W Royal purple sitting around and am wondering if that's the best bet to throw in my rear end rebuild on an 8.8 out of an 89 gt. I've heard mixed opinions on 90w vs 140w. If 90 is what I should go for i'll just hang on to the 140 till i find an application for it.

Its getting near gears, axles and differential.

Thanks


EDIT: Idk if this will help but the car will not be seeing the track. Just a street cruiser.

5.0stanger

I run Royal purple 90wt, and you will need a little less than 3 quarts to fill it. 140 is too thick IMO

Timspony

I've used the 140 wt in some high milage 5L's....no problems! ...Royal Purple is a good syn. fluid & since you're not draggin it, I'd use it up! I don't think you'll need the friction modifer with the Royal Purple....

HACKGT350

i only use 75w 140 syn. in my diff. its what ford uses in all rear diffs now.

crusin92red5.0

i was gonna ask if you had to add friction modifer to royal purple bc i used 90w and didn't put any in. my buddy at the part store said it already had it. can some one verify that for me?

HACKGT350

yes royal purple already has FM in it. you would have known by now if it didnt

PRO50SC

I use 75/90 in mine