Opinions on Transmission Fluid Changes

[hatzie]

For the TH700R4 TH400 TH350 4L60 4L80 3L60 or 3L80 in good condition fill with Dexron VI.
There is no such thing as Dexron III certified anymore. In 2006 GM stopped buying and licensing it so there's no guarantee it's Dexron III anymore because the fox is watching the henhouse.

Here's GM Tech Service Bulletin 04-07-30-037D on the "new" Dexron VI transmission fluid. Our trucks fall into the "2008 and Prior GM Passenger Cars and Light Duty Trucks" category...
It's worth reading the recommendation to not use Dexron VI in Power Steering, Manual Transmissions, and Transfer cases that originally called for Dexron III. It obviously doesn't apply to the SM465 or the NP203 & NP205 transfer cases that had other fluid recommendations.
The GM recommended juice is noticeably less expensive than the Exxon Mobil product I would trust.

"The content of this bulletin does not apply to manual transmissions or transfer cases. Any
vehicle that previously required DEXRON®-III for a manual transmission or transfer case
should now use P/N 88861800. This fluid is labeled Manual Transmission and Transfer Case
Fluid. Power Steering Systems should now use P/N 9985010 labeled Power Steering Fluid."