Originally Posted By: used_0il
Its the wording the nincompoops at GM put in the owner's manual that is causing the confusion.
Take a black felt pen and cover "at 1st oil change and after", then it all makes sense.
GM assumes that you will change the engine oil and other fluids all at the same time, and since most people have the dealership perform those duties, it makes sense.
Without running out to my truck to look exactly the recommendations.
For automatic transmissions "at 1st oil change and after 40,000 miles".
Cross off "at 1st oil change and".
When I changed my Diff fluid at 50,000 miles in my Silverado, I also changed my transmission fluid at the dealer. Even though the fluid had 50,000 miles on it-with half the miles towing-it still visually looked good. It should be noted the fluid saw temps over 200 degrees on my trip several times. The Dexron 6 seems to be everything that has been published about it. The Diff also comes with a decent grease in it to my understanding.