Has anyone replaced the seal while the transmission is still in the vehicle? I have read that it can be done, just asking if anyone has done it. 79 Dodge w150, so there is plenty of clearance between the tunnel and trans.

Ive done it on my '66 Charger. Dropped the valve body and tapped it out from underneath. I know there's a special tool for it but I didn't have one.

Don't forget the kick down shaft seal.

I appreciate the input. Trying not to drop the pan again, but it is an option.

Luckily that one is no leaking. But with my luck at will start after I replace the shift lever one, so I may as well kill two birds with one service job.

Vertman if I can find it I have that tool.

Yes. Miller C-3642

Nice. I will see if I can find one locally.

If you’re talking about the selector shaft seal, this is what I used.

I used the tool as well, and as pictured above, I had to use a c-clamp to help reinstall.
I feel like I needed the c-clamp to help get a bite to pull as well.
so as long as you have room for it, you should be fine.
also I jacked up that side to get most of the fluid to the passenger side to reduce spillage.

but I seem to recall there is supposed to be an inner seal you can't get to from the outside, but I could be misremembering.

Just did one a couple months ago just as described above. Cleaned up the shaft a little before re-install. Replaced both seals.

There is an updated style of shift shaft seal. I have used it a couple of times now when the O.E. style leaked even when new. I don't have the part information handy, I always get it from my local trans guru. But if anyone was interested, I can call him tomorrow and get it.

It has always sealed my problem shift shaft seal leaks.

Ive done it both ways with and without the tool.

IMO, Its just easier to drop the valve body , especially cars with headers

I did it on a 77 Volare (904) without the tool. Just used a pick. It was a pain.

I just changed both seals on my 79' W150 last weekend. I did however drop the pan and remove the valve body for this. I wanted to change fluid, filter, adjust the bands, and I don't have the special tool anyways. My truck had a 1/4" of dirt sitting around the shift lever ( probably why it was leaking), so I had to clean that as well. This was way easier with the valve body removed, and I didn't have to worry about dirt falling into the transmission. Installing the shift seal was easy as I just used a 1/2" nut and bolt with 2 washers. Just have to make sure the seal is square when starting to tighten the bolt. The kickdown seal is probably not as easy with the valve body in, as the c-clip might be a pain in the butt. It's super easy to change with the valve body out, and you can clean up the sealing surfaces then as well. Make sure the kick down seal goes in as it came out, as it almost looks like it should get installed the other way around.
There is lots of room on your truck to use the tool, however, if that's the way you're going to change it.

Thanks for all the reply's and pictures.

I now have a early spring project to do.

I just did a transmission services, filter and fluid. I thought the pan gasket was causing my leaking problem as most the bolts where lose. But after the services, and it still leaking some, I chased it to the seal. I will attack it from the top

With everyone's input and guidance I feel confident I can do it.

I used a small screwdriver to pry out and tapped new one in with a socket. Not much room.

I tried that with one recently and I think I scratched the shaft service and was not able to pry it out. Probably original 1966.

When I dropped the valve body I cleaned up and polished the shaft. There was some seal wear there too so glad I did.