selector shaft leak fix

[red_67f100]

I've decided to write up on this topic since I found very limited info on how to fix a leaky selector shaft on a C4 transmission. Hopefully this info will help other ppl with a similar problem. I have a 73 ford f250 with a 1978 400 engine and C4 automatic trans. I hated seeing tranny oil stains in my driveway. Upon inspection I saw the leak coming from the selector shaft, so I decided to change the outer shift selector shaft seal (the big one in the pic). Keep in mind I had never done this before. I did some research and learned that you have to remove the tranny oil pan, the TV body, and then the large nut inside, and lastly the pin that retains the shaft in place. After removing all this,you can finally remove the shaft and replace the seal. After carefully installing the new seal and reversing the order to put everything back together (Make sure you place the selector shaft in the correct spot on the TV body or else you won't have reverse or any control at all shifting!!!) This happened to me so I had to go back and fix my mistake. A few days later after finishing that job, I still continued seeing leaks from the selector shaft. I was bummed after all that work. So I went back to the drawing board, and realized that the shaft is 2 piece and there had to be some sort of seal or o ring in there. So the next day, I went to AutoZone, o rielly's, and Advance autoparts but no one seemed to know anything about this mysterious o ring and all places told me they didn't carry it. The only thing that would pop up on their computer was the larger seal. I contacted a transmission rebuild shop and they wanted to sell me the whole rebuild kit ( they wouldn't sell me just the o ring). So I just bought an assorted pack of o rings and rtv orange silicone gasket maker. When I got home I started picking at the selector shaft with a sharp pointy screwdriver and found the broken o ring inside!! I then got a new one from the pack I bought that was very similar in size and thickness and test fit it onto the shaft. It fit perfect!! So I carefully removed it and the added the rtv silicone inside the shaft just as an extra protection against leaks, then re-installed the o ring, then added another layer of silicone. After that I added a flat washer (as I had read it helps compress the o ring for better sealing) and finally put the nut to tighten everything in place. I then added more oil to compensate the oil loss from the leak. It's been a month ever since the fix and I can proudly say the selector shaft leak no longer exists on my truck!!!! I have included a pic below of the large seal and the assorted pack of o-rings I bought.

[WarEagle]

Thanks for the info! I have to do this next week