‘64 Hydra-Matic transmission issue

Justin Kleinman

New member
So I’ve been reading about these Hydro-Matic transmissions and boy do they seem strange to me. Mine is the the original normal one labeled P-64 on the side. The shift from 1st into 2nd is a little hard. Shifting between 2-3 and 3-4 and can’t even notice (are they really that smooth?) The biggest issue I’ve noticed came when I went to pull up onto my ramps. The car didn’t have enough torque to get up them. I put ramp extenders on to make it easier. It made it up those, but still couldn’t go the rest of the way. The engine rpms were way up, and I eventually gave up for fear of it all of a sudden taking off and driving off them. The other day I stopped on a fairly steep hill and I really had to give it the gas to get up it.

Does anyone have any ideas for me. I checked my transmission fluid. It looks really clean and overfilled from the previous owner.


Staff member
You are checking the fluid on a fully warmed up engine/transmission after putting the gear selector in each gear and then returning it to park?
Overfilling will cause the fluid to aerate and eventually cause transmission damage.
Try using a long rubber hose and a suction bulb to remove some fluid.
If you dont hear a slippage whine when having the issue the problem could be the torque converter.
You may have to find a transmission shop familiar with old transmissions.


Thanks. Yes I tested it with it warmed up after I had been driving for a while. I’ll try draining some out. Looks like I can just loosen up the fitting where the dip tube enters the tranny.


Active member
Belleville MI
I wish you luck on finding a local transmission shop that knows anything about those old 4-speed TH's!!! I had one in my old 63 Bonneville in the 1990's I had issues with the trans, the only shop that would work on it wanted over 3 times as much as rebuilding a 3-speed TH400. I ended up replacing it with a Turbo 400.

But I will say they are about the smoothest shifting automatic's I have ever driven when they work correctly, I never felt the 1-2 shift, I only noticed the rpm drop during the 1-2 shift after I installed a Tach.

I would also say to drain the fluid to the proper level and see if it helps. I know they are very sensitive to incorrect fluid levels. Also they weigh a ton! so be very carful if you ever remove one. Also the torque converter bolts together for servicing. It turned out that the seal was bad on my torque converter and it was allowing fluid to bypass internally and I had similar issues at slow speeds and you are experiencing. Unfortunatly if it is the same issue it required removal of the trans, and disassembly of the torque converter to replace the $2.00 seal that is leaking.