The TrailBlazer has exactly one transmission unless it's an SS - the 4L60E. The SS has a 4L65E which has some strengthened components. The 4L60E is notorious for a sun shell spline failure which causes 2,4, and reverse to fail. the 4L60E is behind virtually every 1/2 ton truck/SUV GM has made in the past 20 years. The previous 700R4 was virtually the same with less electronic controls. There may be differences in the torque converter from the V8 to the I6, and different outputs depending upon whether or not it is a 2WD or 4WD.
Sorry for all your problems. I've had a 2002 TrailBlazer that I bought 6 months used and 26K. It has been the best vehicle I've ever owned (I've had 2 Saturns, a Honda Civic, Nissan Maxima, Toyota Camry, and VW Jetta TDI. I have had a few problems including bad lower ball joints, bad sway bar links, and a bad fan clutch. Considering that I have a LTZ with all the features, the fact that everything still functions perfectly at 168K miles makes me smile.
As others have mentioned, very few cars go without at least some problems, and compared with the cost of replacing the vehicle, the money spent is very small. My Civic beater was the most expensive car for repairs. I had more go wrong with it in the 2 years I had it, and spent far more money than I've spent on the TB. The Jetta required more than 5K in work while it was under warranty. Even the Maxima and the Camry required their fair share of out of warranty work. Most of the things I get fixed are small problems. I am particular about problems and as soon as I find one, I get it fixed to avoid bigger problems.
I do know that TrailBlazers weren't the most reliable vehicles GM has ever made, but they are far from the worst vehicle out there.