Got a 69 Roadrunner 727 auto. I need to replace
the shifter shaft seal. How best to do it?????

I had the same problem with the 727 in my 68 C body, I dropped it off at a good trans shop.
They pulled the pan and the shaft out and pushed a new on in from the top. About $75 with new fluid and filter..
He said he had done a couple previously..

Easiest? (Besides paying someone else) is to drop the pan and valve body and press in a new seal. Not difficult, but a fair amount of work and VERY messy.

Less mess? Just remove the linkage, pry out the old seal (not much room to work--I've done it on a Volare) And press the new seal over the selector shaft using a deep socket and big C Clamp. You can dress the shaft with some 600 grt sanpaper if you think its corroded at all (after you remove the old seal).

If you try this method and you can't get it, you haven't really lost anything, Plan B then becomes dropping the pan.....

I assume you want to do it in car!
pan and valve body off. then tap it out from below.
then using a piece of 3/8 threaded rod and large washers you set it in place then put rod up through with big washers on top and then a nut on using the threaded rod to pull it down into place!! Think I used a big socket on the bottom has to be bigger than the hole.

Here's the info you need, pretty easy to do.

https://board.moparts.org/ubbthreads/show...&PHPSESSID=

they actually make a tool for this.
Big pipe like piece with threads on the end that grab the seal and pull it out.
Then a socket type tool to help press in the new one with a c-clamp.