Abstract: A transmission assembly for enhancing the performance of an internal combustion engine or the like, the transmission assembly including a coupling plate mounted between first and second automatic transmissions; a drive shaft disposed in driving relation with the first and second automatic transmssions; and a conduit for providing pressurized transmission fluid communication between the first and second automatic transmissions. Each automatic transmission further has a shifting lever which permits an operator selectively to actuate each transmission in a predetermined fashion, as appropriate, to highway conditions or other operational considerations.