My 2003 2500HD manual calls for 80W-90 in the front axle and 75W-90 in the rear axle. Is there a synthetic lube that is approved by GM which I could use in both axles?

The rear diff. oil IS already synthetic. The front is not. I suppose you could use the synthetic oil in both front and rear.

I use Mobil 1 in both ends. Later! Frank

You can use synthetic in both. Look in the TSBs and you will see one on the front diff where you need to change the vent cap if you go with synthetic due to a compatibility issue with the materials.http://www.dieselplace.com/forum/smileys/Geek.gif

Ditto with above, the same synthetic in the rear can be used in front with no trouble, just change the diff vent cap

Does anybody use the heavier oil in the rear axle I think its 80/140w? I thought it was an option if you do a lot of heavy towing.

Kid:I bought a Mitsubishi Fuso truck for my business a few years back and it came with the 140w gear oil. The truck came from California and the service manual stated that the heavier weight was for year round sustained hot climates(100 plus deg) and heavy loads. I know this is an apple and oranges comparison but the same may hold true for our trucks.I'm sticking with the 75-90w mobil 1 synthetic.


No worries here.http://www.dieselplace.com/forum/smileys/Approve.gif

I use Red Line sythetic, front and back..

http://www.uscom.com/%7Ehoot/cars/duramax/gmc/mag-hytec/images/DSCN1163.jpg

http://www.uscom.com/%7Ehoot/cars/duramax/gmc/mag-hytec/images/DSCN1164.jpgEdited by: hoot