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I have a leaky selector shaft seal on my Ultramatic, which is not uncommon from what I understand. I replaced it once last year, without much improvement. Now that I look back on pictures and blow them up I see the issue is the shaft is damaged. Either the seal is getting damaged going over this damaged area, or the damaged area goes in far enough that it is under the seal.

I had assumed that that damage is on the shaft and that it has a shoulder there, but is it possible that the shaft has a speedy sleeve on it?




"IF" I wanted to remove the shaft and have it repaired, is it possible to do this while the transmission is in the car? Can it be removed by dropping the pan, removing the valve body, etc.? Or, can this only be accomplished by removing the transmission.

I suspect that the oil level is below the seal when the car is running and that leaking primarily occurs once the car is parked and the oil level in the sump rises.

Actually it's impossible, within reason, for exterior f***ery to damage the seal as the seal never passes over the end of the shaft. How long since it was last rebuilt? It could just be old. Who knows what someone was trying to do to that shaft. Was Godzilla using it as a toothpick?

As I think you have heard by now, you have to drop the trans to get that shaft out, or cut a hole in the frame.

I have no explanation for that brass area. The shaft should be solid steel. Side note, that bolt is not original, but it matters little. You might get more play, faster.

Any potential leak in the transmission will leak eventually as the fluid gets sprayed everywhere and is good at working into gaps. But that's a reasonable assumption; I forget how high the fluid is in the pan at rest. I know if I was designing something I would try to keep the level below as many sealing surfaces as possible. But the trans, converter, and lines holds 12 qts somewhere...

HPH, thanks for the reply.

I have no idea if, or when, the transmission may have been rebuilt. I did manage to replace the seal last year, not a simple task, but the leak is about the same.

Yes, I understand the complications involved with getting the shaft out. I think it will stay as is for now unless the transmission needs to come out for another reason, such as rebuilding.

Should the bolt be a grade 8 rather than a grade 5?

I think once the converter drains the oil level is above that seal, and is probably below when the car is running. That is, the leaking is probably occurring more when the car is parked than when it is running.

Oh well, a project for another time! Going after leaf spring next to see if I can level up the back of my car.

No, it's because the original used a pointed set screw and jam nut.

Did you polish the sealing part of the shaft with Scotchbrite before install? Did you confirm the bore condition? Some Indian Head Permatex around the bore before you press in the seal will help things. Of course there should be no burrs or gouges.

Not so fast. Those levers were split and clamped on with a bolt to tighten. It is fine. You can see the splined end of the shaft. But the booger marks are going to have to go to stop the leakage. If not too fainthearted, take some careful measurements and cut an access hole in the crossmember with a holesaw. There are endless numbers of good used shafts available.

Side note, this post reminded me that on the twin ultras, the oil only gets "1 quart above" the rear case plug, with 11 qts stored below (unless your pan is bashed in from some off-roading). 😉

That plug is right around the level of the seal, so that makes sense it would leak when still.