The "Ultradrive" was used in the AC Body,AA Body,Shadow/Sundance,Acclaim/Spirit,ect...It is the world's first fulluy adaptave ,electronicily controled,four-speed automatic transmission.It "fine-tunes" itself, constantily sensing changes in speed and driving.Electronically and automaticaily.Ultradrive shifts into precisely the right gear at precisely the right moment.The result is a remarkably smooth ride, enhanced engine performance, and impressive fuel efficiency.And because the adaptive controls in Ultradrive also compensates for fluid changes, engine changes and internal wear...its performance remains dependable after years of ownership. Unfourtaunatily, the microprocessor in the transmission messes up. So, you have been warned. The model number is A-604. DO NOT GET THIS TRANSMISSION!!! It is alot of headaches