Muncie Transmission Countershaft to Case leak

[Richard M.]

This on a '67 L71.

Front of the transmission was leaking, and apparently for a long time, so I pulled the transmission, wiped the front area, tilted forward and let it rest overnight. I see where the leak is. I thought it was the front bearing retainer gasket. It is not.

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It's the Countershaft to the Main case. After research, I see that it's a press fit into the case. I did some more archive searching and word is that it could be a egg-shaped case and that a bushing should be installed. I read that HERE.

I have neither the time nor the experience to attempt to get into a rebuild on this unit. I'm open to a temporary repair and pull it later for overhaul and reseal. I have heard others have sealed the outside after a tilt rearward and good cleaning and using RTV sealer with success.

Or send it out to be corrected but I need it back very soon.

Thoughts?

Another rearward step ...
Rich

[Bob R.]

Re: Muncie Transmission Countershaft to Case leak

I put a thin layer of RTV sealant on my Muncie and have had no issues since. It is a very common issue with these old transmissions

[Patrick H.]

Re: Muncie Transmission Countershaft to Case leak

I'd send it out and have it fixed, as I hate re-doing things later if at all possible. I'm doing something similar with a part from a non-GM transmission, as to have it fixed is less money than finding a new part.

An alternative is a new SuperCase.

[Richard M.]

Re: Muncie Transmission Countershaft to Case leak

A non-mentioned caveat......This transmission is not the original to the car but has the correct casting numbers on the associated items. However, it is in unknown internal condition.

Main case is 3885010, Tail Housing is 3857584, Sidecover is 3884685. It has a P0120 stamp on the main case which I am confused about. There is a stamp on the side rear flange of the case.....G101056. (with a over-struck "5" appearing over a "2"?)

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Am I wrong or right here.......?
P- Muncie
0- 1970 ?
1- January
20- 20th day

If it's January 20th, 1970, I have just read that a "P" for a 1970 case is the Muncie heavy duty case. (ref NCRS 1089 Spec Guide)

I wish it was original to the car. Then the decision would be easier........I'd get it done over and have a bushing installed for the countershaft as recommended.

I drove the car before body-off and it was shifting and acting fine, but you know how things go. As always, it seems what we do not touch during a restoration, usually becomes a problem. Leaks are my nemesis. Probably because of my Jaguar V12 background. If a Jag V12 doesn't leak oil that means that likely there is no oil in it.

I am perplexed with what to do here. Thanks for your guidance.

Rich

[Patrick H.]

Re: Muncie Transmission Countershaft to Case leak

Leaks are my nemesis.

Muncie SuperCase and a rebuild kit.
Rebuilding the M-20 in my 71 was one of the more fun jobs I've ever done on a Corvette. I suspect you'll love it.

[Gary R.]

Re: Muncie Transmission Countershaft to Case leak

Rich,
That is a common issue with Muncie trans. If you want to keep it I would contact Paul Cangelosi, he's in FL or Ed Hartnett to rebuild and repair it. If you don't care about it you can go with the mentioned super case, those are pretty nice but it will change your budget a bit. When I assemble them I use Loctite gasket maker on the shaft, as Paul shows in his books. If the hole is round it will seal but egg shape will require a bushing.

[Timothy B.]

Re: Muncie Transmission Countershaft to Case leak

Rich,

I would tilt it up, clean it with some brake clean and seal it with some RTV. Give it a kiss and put it back in place...

[Patrick B.]

Re: Muncie Transmission Countershaft to Case leak

A non-mentioned caveat......This transmission is not the original to the car but has the correct casting numbers on the associated items. However, it is in unknown internal condition.

Main case is 3885010, Tail Housing is 3857584, Sidecover is 3884685. It has a P0120 stamp on the main case which I am confused about. There is a stamp on the side rear flange of the case.....G101056. (with a over-struck "5" appearing over a "2"?)

[ATTACH=CONFIG]67084[/ATTACH][ATTACH=CONFIG]67085[/ATTACH][ATTACH=CONFIG]67086[/ATTACH][ATTACH=CONFIG]67087[/ATTACH][ATTACH=CONFIG]67088[/ATTACH][ATTACH=CONFIG]67089[/ATTACH]


Am I wrong or right here.......?
P- Muncie
0- 1970 ?
1- January
20- 20th day

If it's January 20th, 1970, I have just read that a "P" for a 1970 case is the Muncie heavy duty case. (ref NCRS 1089 Spec Guide)

I wish it was original to the car. Then the decision would be easier........I'd get it done over and have a bushing installed for the countershaft as recommended.

I drove the car before body-off and it was shifting and acting fine, but you know how things go. As always, it seems what we do not touch during a restoration, usually becomes a problem. Leaks are my nemesis. Probably because of my Jaguar V12 background. If a Jag V12 doesn't leak oil that means that likely there is no oil in it.

I am perplexed with what to do here. Thanks for your guidance.

Rich

It was built January 20, 1966 and installed originally in a 66 Chevelle assembled at the Framington plant. The 3885010 cases were used for 66 and 67 Muncies. The Muncie date code system changed in the 1967 model year.

[Gene M.]

Re: Muncie Transmission Countershaft to Case leak

Rich,
If you are feeling lucky try loctite vs rtv since the gap is so minute I feel loctite will have a better chance of filling the void. Parts have to be real clean. Of corse this is all in lieu of correct weld it up and bore or bore & sleeve.

I know the feeling of wanting to put something together and being held up by the unforeseen.

[Stephen L.]

Re: Muncie Transmission Countershaft to Case leak

Here is a solution to eliminate the shaft leak:
Purchase a new shaft; about $24
Machine a shallow groove in the shaft about .150" from the end of the shaft. (The housing is close to .500" in the area of the hole)
Install an "o" ring with a slightly larger O.D. (.010 more than the shaft). Coat with sealant. Insert the shaft into the case. (interference fit). The "O" ring seals the hole and will also allow some shaft "movement" as it does presently which caused the leak in the first place.
Use "green" "O" rings as used in AC systems. These are not affected by the oil.

[Richard M.]

Re: Muncie Transmission Countershaft to Case leak

Thanks All, I have made my decision. It's in multiple parts.

I will use the sealant method. At a later time I will either have the case flaw corrected using everyone's recommendations, or acquire a correctly dated case or complete unit.

After a scrupulous cleaning I'm going to try Gene's idea using the Locktite and ALSO Bob and Tim's idea using the RTV. I like both ideas so I'm going with both.

I'll drip in some Green Locktite, the type for pre-threaded fasteners as it's very thin. I'll let that cure for several hours then apply some RTV at the edge of the shaft to the case. I'll let that cure.

Then I'll add more RTV at the entire shaft area and before the RTV sets I'll place a small piece of wax paper over the area and remount the transmission to the bellhousing/engine.

I will let you know the result.

Thanks for your ideas

Rich

[Chester C.]

Re: Muncie Transmission Countershaft to Case leak

I've own a lot of these transmissions and they all leaked. Even with a press fit oil can still creep by. I did what was suggested and you never have to worried about it again. And that is put an "O" ring on the shaft.

[John L.]

Re: Muncie Transmission Countershaft to Case leak

I would also suggest cleaning it with brake clean and covering it with an RTV sealer.

[Tom D.]

Re: Muncie Transmission Countershaft to Case leak

I assume some 325 cases were left over and used in 1966 models. Any known details or corrections are welcome. Thanks.

[Richard M.]

Re: Muncie Transmission Countershaft to Case leak

It was built January 20, 1966 and installed originally in a 66 Chevelle assembled at the Framington plant. The 3885010 cases were used for 66 and 67 Muncies. The Muncie date code system changed in the 1967 model year.

Patrick, Thanks for that information. So the "01" is January, and the "20" is the 20th day?

How did you deduce that it was 1966? Was it the "G" prefix in the number on the other side?

Is the "01056" the vin derivative for the Chevelle?

I have a hard time understanding the Spec Guide for Transmissions.

I assume some 325 cases were left over and used in 1966 models. Any known details or corrections are welcome. Thanks.

I don't really follow what you're saying Tom. Can you expand?


===============
Thanks all for your ideas. On rebuild or whatever is decided, I like the O-Ring idea.

I used the Loctite and this morning I applied the RTV. I'll test it for leaks later.

Thanks,
Rich