I want to thank each of you for the help. I think I will follow tech2 and do both filter and Dexron flush on the transmission.

Next question please, what lube for the rear ends in Texas heat?

 

I use Mobile 1 75w-90 in a limited slip rear end.
florida

 

Check your owners manual for recommended fluids, for the 07 and up the recommended fluid is:

Rear Axle
SAE 75W-90 Synthetic Axle
Lubricant (GM Part No. U.S. 12378261, in
Canada 10953455) meeting GM Specification 9986115

 

I have had the same service adviser for some time, so I am hoping he is steering me right.... I believe Tech2 has the right recipe, exchange all the fluid, with the same flow direction and non-pulsed and you should be good....
Regular fluid and filter changes would net you nearly the same thing.... but I have known others with gmt800's that got 230k miles out of a transmission and never serviced it....
I'll setup my reminder to have the filter/fluid changed again at 130k, that will put me on a 50k service interval.... if it fails before then I let you know so you can say I told you so....