Why does my automatic transmission sometimes refuse to accelerate?

David Cox had a problem where the engine RPMs would jump and the car wouldn't accelerate. In his case, it was the torque converter. Dan Henderson also had this problem, but all that was required was to refill the transmission with the correct amount of fluid.

In the case where the automatic transmission works except for the overdrive (4th gear), Kurtis Bredda had the "end clutch" (Mitsubishi part # MD723508) fail. Please see http://www.plymouthlaser.com/ for information on end clutch replacement.