So... here is where I try to go into detail of the problems with three different transmissions that I feel must have somewhat similar causes. The vehicles in question are my 04 Comp G with currently 134k mi, dad's 06 GP with...I believe 199 if not 200k mi now, and mom's Bonnie with approx 160k mi.
*One note, the Bonnie did have a used/rebuilt trans installed back in late 2016 off a Le Sabre that had 80k mi on it at the time, so the trans itself definitely is not as worn as the car and neither should be the fluid as new fluid was obviously added when the trans was installed.*
Mom says the Bonnie usually starts shifting hard 1-2 and 2-3 when the engine gets hot (around 200 degrees really) - since we can't really gauge how hot the trans is apart from the engine that's all I can say there. There have been occasional slips, we think, when accelerating from a full stop, but usually for a split second. Slipping was honestly WAY worse with the original transmission when I had to drive it to school everyday just before we ended up replacing it
The 06 base GP who just made 200k mi or will be very soon - that sheeit gets really hot on my dad's drive home from work. I'm talking up to 230 degrees so far. This is a drive that should be a half hour but usually is a bit more because of traffic on both highway and city, though. This one also normally starts shifting very hard when it starts getting warm - literally feels like the trans is going to crack open with one of those jolts. My dad did try some Lucas for the trans, forgot what it was called, for slippage I believe; it appeared to help immediately but within a few days symptoms came back. We did notice though that shortly after the additive it would sometimes shift hard when it wasn't even that hot (around 160 degrees) or even start shifting normally when it's hot again - which usually was when it would act up. But that was just for the week or so after adding that stuff in, it's back to the usual problem except now it gets way hotter and quicker than it should.
Last but not least (or maybe it is the least affected one?)
My Pumpkin's trans gets warmer than it should too. If we are driving maybe 10-15 minutes straight city or both city and highway combined, I've noticed it has gotten up to 206 highest (so far) - I can only assume it would keep climbing from there if I drove as much as my dad does. In terms of how the shifting feels, definitely nowhere near as hard as the Bonnie or the 06, but you can definitely feel the first two shifts more than you should imo. I feel like they are slightly delayed too, like the engine has to rev longer/higher before it decides to shift. I did have a couple of occasions where it slipped for a split second from a stop, but since doing a fluid and filter change I don't recall it happening again. However, after 8 quarts of the fluid being changed it still gets hotter than I like, sooner than I like. I *almost* feel like it was a waste of $60+ however much I spent on the fluid, then again the fluid was a pale yellow so it needed to be done sooner than later. I did use Dex III. Sorry, couldn't really afford to buy the newer type at the time (kind of still can't, still looking for work)
So, what does everyone have in mind, besides I definitely should've bought Dex VI? Lol.
I just don't want anyone to have to spend money they don't have on another whole transmission- plus I don't even think I could possibly find particularly another tapshift trans around here either if mine decides to crap out on me