6L80 Drain and Fill? Does type of Dex VI ATF Matter?

[clh5411]

Hello all, just picked up a new to me 2016 Tahoe LTZ with 115K. It was very well maintained and garage kept, but I know its still a roll of the dice as far as the lifters and trans are concerned. I ended up doing a drain and fill on the front and rear diff as well as transfer case. I also tuned out the AFM. Next on this list is address the 6L80, which shifts well now for what it's worth, although the previous owner never serviced it over the 100k they owned the truck. I went ahead and put an upgraded thermostat (GM #85585333) that kicks on trans cooling at 154F, which is working great. It never got over 200F before I installed, but every bit helps from what I understand. I did notice when I changed the part and caught a small amount of the trans fluid, it was black. I am considering doing a drain and fill ( or 2-3 of them over the next 15k miles) to try and freshen up the fluid.

Seeking advice here, is it worth a drain and fill? Is it better to leave it alone at this point and keep my fingers crossed? I don't want to stir up problems but at the same time maybe I can avoid some if it's not too late? If I proceed, is there any value to a "high end" ATF like Red Line's D6 vs standard stuff from the store?

 

[Fless]

I think "very well maintained" might not be a very accurate statement. Totally ignoring the transmission fluid for 100k miles is asking for trouble.

I'd say to drop the pan, change the filter, and start exchanging the fluid (regular Dex VI). Whether you do that several quarts at a time or have a fluid exchange done is up to you.

 

[West 1]

New Tranny Oil pans are available that have a drain plug in them for less than $80. If you install a new filter with a pan drop you could install one of the new pans and make it a whole lot easier to change the fluid a couple more times to get it clean inside. This would allow you to swap the filter install a new pan and then do your next couple tranny oil changes without dropping the pan. I wish I had installed a new pan when I had my pan off.