Doing a stall speed test will tell the health of the transmission and most importantly the torque converter. The stall speed of you car should be around 2200RPMs, anything higher = the transmission or torque converter is slipping.
The most accurate method for determining actual stall speed on a car is to launch the vehicle at full throttle, flash stall and note the rpm at which the car actually takes off (requires a partner watching the tach). the owners manual will tell the speed of each
selected gear.