[farnorthdriver]

Am changing out my front diff oil.
The way I see it, a 75-90 synthetic is called for.
As things seem to change (and some times improve) was wondering if anybody can confirm this .....or is there someting better being called for now for the front diff?

--My rear diff (a Dana 80) has Mobil 1 75-140 in it but I'm figuring I should not use the 75-140 in the front diff, right?

Thanks!

 

[JasonL]

The front does need 75w-90, not sure if synthetic is reqiured, but I use it and feel it's probably a good idea. I wouldn't put a 140 in the front, 90 will be just perfect. I also use Mobil 1 synthetic, and I change my diffs about every 40k and it still looks brand new, but cheap insurance IMO.:thumbsup:

 

[txgp17]

I wouldn't put a 140 in the front...

Not trying to contradict you, but why would synthetic 75W-140 be a bad choice?

 

[JasonL]

Not trying to contradict you, but why would synthetic 75W-140 be a bad choice?

I like to run everything in spec, according to the manufacturer's recommendations. 140 is a bit thicker and it may be ok for some, but for most I believe it's best to stick with what Dana and Ford specify. The Sterling rear does require 140 synthetic, would be nice if they kept it uniform.:lol:

Just a little caveat, however, I don't like to keep 'exactly' to their recommendations, but just for things like never changing the rear diff oil. I know Ford claims it's lifetime unless you get water in there, but I just can't jusity that for such a cheap and easy job.

 

[txgp17]

...would be nice if they kept it uniform.:lol:

Sure would. I bought the necessary amount of Valvoline synthetic 75W-140, and dumped it in both. The mistake I made was adding Lubegard's Limited-slip additive to the Valvoline, which already has the LS additive in it. Now my limit slip is an unlimited slip.

 

[JasonL]

Sure would. I bought the necessary amount of Valvoline synthetic 75W-140, and dumped it in both. The mistake I made was adding Lubegard's Limited-slip additive to the Valvoline, which already has the LS additive in it. Now my limit slip is an unlimited slip.

Hopefully someone with a little more knowledge will chime in here then, perhaps you are ok with 140 up front. I was happy when I changed my rear diff with the Mobil 1, didn't have to add any friction additive. My dad's classic Chevelle has some synthetic in it (Redline maybe) and it's ALWAYS a guessing game to get that additive at the perfect level, my truck was never as picky though. Old cars sure are tempermental...:lol: