Shot Gun Rich

Is the 1954 & 1955 Pontiac hydromatic transmission the same as oldsmobile 1954 & 1955 hydromatic transmission. I'm in need of a oldsmobile hydromatic

Tedd Thompson

Same transmission but different bell housing pattern. Are you looking for a driver or a rebuilder core? I may have a core or give John a call 2 blu 442 he had a couple of 54-54's he was parting out...Tedd

rocketraider

As Tedd says, same transmission. The bell housing adapter is different, but you can transfer the Olds adapter to the Pontiac HMT.

Shot Gun Rich

Ok thank you, to make sure if i end up using a Pontiac hydromatic when & if it needs internal parts , I would order Pontiac hydromatic parts or olds would be exactly the same ?

Charlie Jones

While Pontiac and Olds both used the Hydra-Matic trans there are some differences in these transmissions.
As mentioned, bellhousings are not the same. Also tail housings and rear yokes may not be the same.
Gear ratios also may vary, so gears may not be the same. Govenors and valves that control the shift points may also vary.

If you're going to try using Pontiac parts in an Olds trans get a Pontiac parts book and an Olds parts book.
Look,up the part in question in both books. if the part number is the same it will fit.
If the number is different then probably not.

Shot Gun Rich

Ok thank you

redoldsman

It might be worth you time to call Fatsco since they are the leader in vintage transmissions. Charlie won't steer you wrong either.

d2_willys

Some things to know:
1955 and 1956 Pontiac hydramatics are slant pan types, but not 1954's. Olds used slant pans from 1954 to 1956.
Here are other differences:
1) Pontiac had a lower first gear ratio
2) Olds started in 1st when in lo range. Pontiac started in 2nd.
3) Pontiac used 2 bellhousings, where Olds used one. Even though both were slant pans, the bellhousings were different.
Given the above information I would examine and make a decision.

Shot Gun Rich

Thank you everyone for all the great info.i did find a 55 olds hydromatic. I just saw on one of the hamb blogs something about Putting a 1955 olds engine with the 55 crank against a 56 jetaway trans that the 55 crank is different has a smaller pilot hole.

Just wondering would I have any issue though putting the 56 engine with the 56 crank against a 55 Hydromatic ?

d2_willys

It depends on what 56 transmission was connected to the 56 engine. If it was the R56 hydramatic (has side cover like the 55 hydramatic) then everything should be fine. However if it had the O56 Jetaway hydramatic, you will need to install a pilot bearing/bushing for the 55 hydramatic input shaft to mate to the crankshaft. I took my 371 crankshaft to a machine shop to have them install a pilot bearing. This was while I was rebuilding the engine. The crankshaft was out of the engine and the journals hadn't been machined yet.

Shot Gun Rich

Yes my engine has the jetaway on it right now.do you know where I can get that pilot bearing for the hydromatic or does any engine machine shop will have one.i am gonna have the engine rebuilt

Charlie Jones

The factory number was 412562 that crossed over to this;
Dorman 690-014.1: Clutch Pilot Bushing [1946-2000 GM - 1966-1971 Chrysler - 1968-1982 Checker Motors] - JEGS High Performance

Shot Gun Rich

Thank you