Got good information on the engine and syn oil. Now, justs 2 questions. can I, or should I, use the same syn oil in the front diff that is in the rear? (factory stuff). This is a 03 D/A GMC.





#2 Is the rear end syn fluid also good to put in the transfer case? Need to get all this done as I have 13,000 on the truck already and going to tow heavy next month. Thanks Love the info on this forum. Don

The same front & rear synthetic is is fine for the diffs. If you don't already have the white vent cap (Part #12479296), make sure to change to this on the front diff to support the synthetic.


I used the Amsoil 75w90 in both the front & rear diffs. 1.83 quarts in the front & 3.62 quarts in the rear.


Don't put rear end synthetic in the transfer case. It requires 2 quarts Dextron III or equiv synthetic transmission fluid.