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".
Cee-Jay
2004 Mitsubishi Endeavor XLS
2001 Infiniti I-30t