Hy guys, Hotrod Lincoln is correct, in that no two coupling Hydramatics were ever used in trucks. the truck Hydramatic oil pan has 12 holes, and is 13 3/8" X 10 3/16", the two coupling Hydramatic oil pan has 15 holes and is 15 1/2" X 12 5/16". Incidently there were two different Hydramatics offered in 1956 Oldsmobiles, the type "R" which is the older dual range Hydramatic [same as the transmission used in the truck], and the type "O" which is the two coupling Hydramatic used up to 1959. I haven't been able to locate a detailed enough description of the transmission in question, to say whether the "overunning band" is adjustable or not, but I will keep looking.
