I plan on changing my axle fluids tomorrow, and while at the dealer to get the special white ventcap for using synthetic oil(which they covered under warrantyhttp://www.dieselplace.com/forum/smileys/Clap.gif) i didnt pay enough attention the gear oil i picked up....I got 2 bottles of 75w-90. I know im set for the rear, but the book says to use 80-90....Is there enough of a difference to warrant holding off on doing the front til i get the correct fluid..?
The fluid is just the GM "grape juice" type. Thanks guys...-Adam

There's a TSB for trucks operating in cold climates that specifies the 75w-90 synthetic for the front differential.


I can't imagine there would be a problem running it as long as you've got not only the white cap, but the new o-ring that's resistant to the synthetic oil, but maybe someone here has a different idea?


For what it's worth, I'm gona put it in my front diff when I change it...http://www.dieselplace.com/forum/smileys/Ermm.gif

The 80-90 would be dino oil. The 75-90 is the synthetic equal and is the correct replacement. The 75 rating is due to the synthetic having better flow at lower temps.

I forogot to mention that my dealer gave me the TSB on using the synthetic. Im pretty sure i saw a oring on the new one....Thanks for the info guys....Time to get dirty....http://www.dieselplace.com/forum/smileys/Big Smile.gif