Lock-up Torque Converter

Your torque converter has a locking clutch that is engaged by a solenoid and control by the computer. It senses load and speed to decide when to lock the converter. This solenoid can be sticking which will cause it to stay in lockout. to long. What does your tranny fluid look like is it nice and reddish pink or more brown in color? One good test is to take a clean white cloth and wipe the tranny dip stick down. If you have a lot of black or brown on the cloth you have excessive wear in your tranny. As far as the speed at which the torque converter locks do you remember what speed it locked out before? Under light or no load it should around the 45 mph mark give or take a few.