My daily driver right now is my wife's 2007 Tahoe. Just recently I have noticed that it has started to flare up on the 3-4 shift. 180k miles and honestly..... I have never serviced it in the 100k miles we have owned it and I know it wasn't done by the previous owner. It hasn't been an all the time thing but after taking a trip to the mountains this past week, it showed itself a good bit while climbing up hwy 16. I also kick the tow/haul on when going this way to keep it out of 4th. Started to notice a flare up in the 2-3 shift but not as much. Friend of mine that goes into transmissions more than me suggested to service it, lucas , and the trans go orange box. I plan on getting it rebuilt or replaced but need it to hang on a little while longer. No slipping at all. Trans temps going up the mountain were never over 215* and they stayed under 200* the rest of the trip.