If my memory is not failing the last 4spd. hydro was 1956 and it went to what was called a slim jim alum. 3spd. in 1957 I know in 1952 the hydro plant burned down and olds and cad. and buick and pont. came with dynaflow trans I bought a 53 olds.in about 1959 and pulled the motor and trans and rear end to put in my chopped and channeled model a coupe and making the trans work right was a night mare because the detents were in the steering column and of course I had already scraped it along with the rest of the car (lesson learned the hard way seems that's the only way I seam to learn ha ha ) any way that other lever is throttle pressure or tv valve ....ted