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64 Grand Prix automatic transmission issues
1. How many models of automatics were installed in 64 GP's with a 389 4V. If more than one, how can I identify what I have?
2. This transmission pukes out fluid in large amounts sometimes after operating the vehicle, then other times it won't. What might that be?
3. In 2nd gear with light accelleration the car has a mild lurching sensation almost like an engine miss, but when it hits 3rd it runs strong and smooth.
Any ideas there? I've been told it is a common quirk but I can't buy that.
4. Also the chrome console shifter gets very hot during operation. The longer its driven the hotter it gets. However the fluid that stays inside the transmission is still red and
doesn't smell burnt like the trannny is severely over heating.
Note: Car has been stored for sixteen years and only been started and driven once or twice a year during that time.
OK Pontiac gurus, step up and lay some expertise and advice on me because I'm baffled by it all. Thanks in advance for any help!
posted: September 13, 2008
  Answers (3)
all i am able to find is that there was only a roto hydra-matic. but in the the standard catalog of pontiac it mentions something about a roto hydra-matic that caused slightly less horsepower than the other roto hydra-matics. it is referred to as HM 61-10 "Slim Jim" transmission.

the roto hydra-matic is all i see in my hollander book too.

i hope this helps.
sources: standard catalog of PONTIAC
posted:  September 15, 2008
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Here's my 62 Catalina, it has a "Slim Jim" (roto trans). I just had it rebuilt because I wanted to keep it all stock. This trans was used on Pontiacs and Oldsmobiles as an ECONOMY package. Usuall with a 2bbl carb and a single exhaust. Mine was puking a little fluid as well. There is a seal on the dip stick that is supposed to keepm the fluid in. There is an adapter, i'm told that will allow you to put either a 4 speed manual or any number of GM automatics (200r4,359,400 or 700r4 ???) The Bonneville had a true hydramatic trans.
posted:  October 6, 2008
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Thanks for the input guys. I will definitly check that dipstick tube. Don't know why I didn't think of that as I have had that problem before with another vehilcle. Guess at 56 I'm starting to go senile. Mine is a 389, 4 barrell 303 HP with a 26K engine code so I don't think I have a Slim Jim trans. Any how Thanks Again
posted:  October 6, 2008
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