My understanding is that the GM 4L30-E transmission in the Troopers is much better suited for lighter duty vehicles and, as a result, problems with this transmission in the Troopers are relatively common. Also, the 4L30-E is allegedly a PITA to service properly, which probably contributes to the problems.
Plenty of guys who take good care of them get good performance even while running larger tires in off-road situations, but scanning craigslist for used Troopers it appears very, very common to find vehicles with only 100k to 150k on them advertised with "just replaced transmission".
2004 Mitsubishi Endeavor XLS
2001 Infiniti I-30t