I have no technical knowledge of the dual coupling HydraMatic used in the '56 through '64 (or so) Pontiacs (Cadillacs and Oldsmobiles). I'd pose your questions to the whole forum in the 60 & Older section and hope that SteveP answers. He's the expert.

Bill, I just joined this forum and recognized your name from a Chevy truck forum. Since you were sort of a "familiar face", I thought I'd run some questions by you. Yesterday I bought a 1957 Pontiac Star Chief with a 347 engine and Hydramatic transmission. The transmission shifts really hard into 3rd gear, and if I get on it a little bit the transmission slips and makes an unusual noise. How hard are these transmissions to work on? Are parts readily available for them? If all else fails, can I swap it out for a TH350 or another GM transmission? I know that's several questions, but I know very little about automatic transmissions. Thanks for your response.