not this Gen, but I have a 96 with what I believe is the original 4l60e with 325k miles on it. I dropped the pan and did the filter when I first got it, like 20 years ago at this point with high 100k range I wanna say 175k but not sure, it's been forever ago and 3 states haha. but since then I've used the vacuum extractor to suck out the fluid from the dip stick and top it back off. it only gets like 3 or 4qt out, but done it probably 5 or 6 times now. it's still going.
funny it's had a slight delay to shift into reverse since I got it, when I first got it it was like eh, it will need a tranny soon but it's a good deal. so I picked it up. still going all these years later.
I feel like good fluid is the best thing for these trannys. that and keeping them cool. mine has the tow package, so all the extras coolers.
my 2011 has the hybrid tranny that I believe is based off a Allison hybrid bus tranny tech back then, just smaller in a multi manufacture collaboration to bring it to the truck world. 145k, never seems to get over 167deg even when towing, doesn't have a torque converter but does have some electric motors and some veritable gear ratio thing going on. so no clue what the life expectancy of it is, but I plan to keep fresh fluid in it and just got a test sample back from Blackstone labs and it seems all is good wear wise from there.
if you're curious, a fluid sample test will tell you a lot about what kinda wear you have going on.
