What causes a Chevy Trailblazer transmission to overheat?

Three problems I know of are one not changing and/or checking fluid level and if you do alot of hauling the more weight the warmer the fluid get and finally the more shifting you do (mostly city driving) the warmer the fluid gets.ni

Make sure your lockup torque converter is functioning. It has to work in overdrive or it will overheat. When your torque converter locks up, you have a mechanical link between the engine and rear end. When the lockup torque converter isn't applied, you are coupled from the engine to the rear end through fluid which can churn and overheat in steady driving in overdrive.