I wrote a previous post about about my transmission leaking and the process I took to locate the source of the leak. My dripping ATF problem stemmed from the shift shaft seal.

My car is an '85 with the 700R4 automatic tranny.

I just finished pulling the old seal and installing a new one. This was not the easy fix I expected it to be. I watched a number of videos and it looked like a 15 minute job. ROFL. bahaha. 15 minutes... didn't quite turn out that way.

The first day I worked on it, I just couldn't get the old seal out. Frustrated, I quit and went back in the house to rethink my failed strategies and spend some time with my good friend Jack Daniels. Today, I went back out to the garage fresh and determined and was able to get the seal replaced. Jack and I will be celebrating tonight.

For those of you who end up with a bad shift shaft seal and decide to tackle the repair, it's doable but needs some patience.

The video link below shows the process using the seal removal tool to get the old seal out and new one installed.


It's that simple IF you have the tranny on a table with lots of room to move around. You will find out that space is tight around the shift shaft and the exhaust pipe is perfectly placed to make this job miserable.

There are no doubt a number of ways to get this job done. This is what worked for me in the end with lessons learned along the way.

I did this job, in my garage, with the car on ramps, on my back, with the transmission in the car.

HOW TO GET THE CURSED THING OUT AND BACK IN

- remove the nut holding the shift linkage to the shaft. I found that also removing the 2 bolts holding the linkage bracket to the transmission pan allowed the linkage to be moved to the rear creating much needed hand space to work.

- I ordered a seal removal tool from Amazon. It did not fit the shaft. The interior diameter of the tool was too small. I could see it making contact with the face of the shaft. I had to Dremmel out the interior diameter until it would slide easily over the shaft. Don't pound on the tool to get it over the shaft. You will damage the shaft creating passages for future leaks.

- There is NO room to swing a hammer to seat the tool into the seal. I removed the bolt from the tool. I used a small flat pry bar leveraged against the exhaust pipe to put pressure on the back of the tool while I used a wrench to slowly turn it until the threads made their way into the seal. I then put the bolt in the tool turning slowly and started to back out the seal. Once it was properly seated in the seal, the tool worked slicker than goose shi#t.

- I cleaned the shaft and inner surface of the bore on the casing with a 3M Scotch-brite pad and a spray of brake clean when done.

- I lubed the new seal with ATF and carefully placed it on the shaft over the lip edges. I used a 1/2" drive 1/2" socket to drive the new seal into place. Sockets come with different wall thickness so just make sure your socket fits inside the bore opening and the threaded bolt has room to extend into the socket. I wouldn't exactly call it driving the new seal in. Remember there is NO room to swing a hammer. It was more like 100 half inch taps with the side of a hammer until it was fully seated. You will be able to feel when it has bottomed out in the bore.

If you end up with the dreaded leaking shift shaft seal, hopefully this eases your pain during the repair.

Cheers



Nut holding the shift linkage to the shaft.




Linkage removed exposing the shaft seal. ATF can be seen leaking at the bottom of the seal.




Chinese knock off removal tool that had to have the inner diameter enlarged to fit over the shaft. I did not use the included seal. I didn't use the silver installation driver. It was too long. I used a socket.




Removal tool seated in the seal. The bolt was removed for installation.




Bolt reinstalled to pull seal.



... and with very little effort, the seal backed right out.




A good cleaning of the shaft and bore with Scotch-brite and brake clean.




Ready for a new seal.




AC Delco seal.




Lubed with ATF and carefully inserted past sharp edges.




New seal fully seated.

 

I was going to try to change mine a couple of years ago and came to the conclusion that doing it on jack stands was not an option for me. I took it to a very trusted trans shop. They refused to change it from the outside. They said the shaft gets a ridge that must be ground off and polished. This required dropping the pan. I let them do it their way and no leak for a couple of years. More money though. Dan

 

That's definitely the easier option. I did consider it for this job but I hate parting with my hard earned green backs when it's something I think I can do. I would like to know where the ridge supposedly develops on the shaft. The part of the shaft that was visible outside the case appeared to be in good condition on my car. I haven't had a chance to drive it or check on the effectiveness of the new seal installation. If it does still leak, I will place a second seal against the first as '7t1vette' suggested. I'll report back once I have time to crawl back under the car.

 

He showed me a shaft with a ridge too bad to grind. I can't remember where it was on the shaft. Dan

 

And this ridge contributes to a leaking seal? hmmm. Sounds like in that case, a shaft replacement would be the wise fix. This doesn't sound like a common problem. Most just replace a seal and are good to go. Thanks for the input Dan.

 

I agree Bear. It was hard for me to believe a ridge really formed with a shaft not turning much and turning slow. But, I do trust the shop. Plus, I don't think I could have done it with jack stands. You will probably be just fine. Dan

 

Yeah, I'm a little skeptical on the ridge theory when you consider that shaft is static and only moves a few degrees when you place the car into gear on an automatic transmission. Who knows? I have come to learn that many things are possible... but most are unlikely.

 

Well I'm very happy to report that the shift shaft seal replacement seems to have resolved the ATF leak.
I took the car for a ride shifting through 1st, 2nd, Drive and OD several times. Crawled under the car and found no sign of leaking from the shift shaft.



So far everything looks dry. No sign of the red demon ATF.