C4 transmission fluid leak

I have a 66 C4 transmission in my 64 1/2 Mustang convertable. Whenever it sits for a while, the fluid in the torque converter drains back into the transmission and leaks out around the selector shaft. Is there a way to correct this with the transmission still in the car?
If I do have to remove the transmission, what do I have to do to fix the leak?
The transmission is great otherwise

Have a look , 2 seals in that area . Likely it is the small outer seal for the kickdown lever , is easily replaced incar by removing the 1/2" nut and lever , dig the seal out and put in a new one ..

Originally Posted by zigmont

I have a 66 C4 transmission in my 64 1/2 Mustang convertable. Whenever it sits for a while, the fluid in the torque converter drains back into the transmission and leaks out around the selector shaft. Is there a way to correct this with the transmission still in the car?
If I do have to remove the transmission, what do I have to do to fix the leak?
The transmission is great otherwise

I have had some experience with the same problem. This was with a TCI C4 Streetfighter I bought new from TCI. It puddled transmission fluid on the garage floor everytime I drove the car.

You can change the selector shaft seal with the transmission in the car, but you must drop the valve body out the transmission. You can get a new seal at any auto parts store. The kickdown lever seal is just an o-ring and easy to change without opening the transmission.

Yes, I was angry that I had to change this seal after paying about $900 dollars for the transmission. Not only that, but the second time to the strip the forward drum inside the transmission split in half. I have since installed stronger built transmission from a different supplier.