66 transmission - tail shaft housing extension leak

[David M.]

I have a correct Munich 4 speed with casting #3885010. There is a minor leak that appears to be coming from a pinhole in the tail shaft housing extension that drips onto the transmission. It appears to be cast iron but the judging manual says it is unpainted aluminum. See pics below. Any ideas on how to plug the pinhole leak?

[Edward J.]

Re: 66 transmission - tail shaft housing extension leak

David, you drive the pin up and use some brake cleaner to remove any oil and, use some sealant pin and reinstall.I like permtex right stuff.

[Joe L.]

Re: 66 transmission - tail shaft housing extension leak

I have a correct Munich 4 speed with casting #3885010. There is a minor leak that appears to be coming from a pinhole in the tail shaft housing extension that drips onto the transmission. It appears to be cast iron but the judging manual says it is unpainted aluminum. See pics below. Any ideas on how to plug the pinhole leak?

David------


The extension housing is cast aluminum on ALL Muncie transmissions. What you picture on the reverse shift lever boss are not cracks. These are features of the casting and are VERY common on these castings. You'd be hard-pressed to find one that does not show these. They may also be seen at other places on the casting but they appear more like cracks on these bosses.However, in the center of your picture is the bottom of the tapered drive pin that goes through the boss. It looks a little "buggered up" in your photo. If the drive pin is installed improperly or with too much force, it will usually crack the boss. I cannot actually see a crack in the photo but there may be one there or a distortion of the drive pin hole. These could cause a leak.

Otherwise, a leak could be caused by a worn shifter shaft lip seal.

[David M.]

[David M.]

Re: 66 transmission - tail shaft housing extension leak

Joe, thanks for the reply. See my reply to Ed above. There is a small pin hole which I might try JB Weld.

[Joe L.]

Re: 66 transmission - tail shaft housing extension leak

Joe, thanks for the reply. See my reply to Ed above. There is a small pin hole which I might try JB Weld.

David------

If the surface is properly prepared and cleaned, I think JB Weld will work fine. However, be advised that if you cover the tapered pin, removing it later might be very difficult.

[David M.]

Re: 66 transmission - tail shaft housing extension leak

Joe,
Any other suggestions to stop the leak as opposed to JB Weld? Also a dumb question but what is the tapered drive pin for?

[Joe L.]

Re: 66 transmission - tail shaft housing extension leak

Joe,
Any other suggestions to stop the leak as opposed to JB Weld? Also a dumb question but what is the tapered drive pin for?

Dave------


You could try an oil resistant silicone sealer like Ultra Black or Ultra Copper. I would slightly roughen the entire surface around the suspected crack, then thoroughly clean with brake cleaner. Finally, apply a coating of the sealer and let cure.

[Gary R.]

Re: 66 transmission - tail shaft housing extension leak

I am rebuilding a '65 M-20 now and the rev boss tapered hole was chipped and had a crack 180* around it. I had it welded and finished it.

[Joe L.]

Re: 66 transmission - tail shaft housing extension leak

I am rebuilding a '65 M-20 now and the rev boss tapered hole was chipped and had a crack 180* around it. I had it welded and finished it.

Gary------


This kind of crack is usually caused by someone trying to drive out the tapered pin from the wrong end or using too much force to drive it in.

[Gary R.]

Re: 66 transmission - tail shaft housing extension leak

Joe
Exactly what happened, this trans was worked on before. I have the boss repaired now and the pin fit good.

[David M.]

Re: 66 transmission - tail shaft housing extension leak

Gary,
What is the purpose of the pin?

[Joe L.]

Re: 66 transmission - tail shaft housing extension leak

Gary,
What is the purpose of the pin?

David------


The pin passes through a groove in the reverse shifter shaft and thus retains the shifter shaft in the housing. In order to remove the shifter shaft, the pin must first be removed.

[David M.]

Re: 66 transmission - tail shaft housing extension leak

Makes sense. Thanks.