67 M20 input shaft seal?

[Greg L.]

This is my first time ever working on a Muncie so please bear with me.

While changing the clutch on my brother's 67 Camaro I figured that I would try and stop some of the leaks which look to be mostly coming from the shifter shaft seals but I figured that I might as well change all the seals since it was out. So I pulled out my 69 service and overhaul chassis manuals and started to take things apart.

I pull the side cover off and except for very fine bronze looking particles in the oil(which I assume is normal...right?), it all looks good. Then I take off the brg retainer for the input shaft to replace that seal and....there is no seal...?? There isn't even a machined surface on the shaft for a seal to seal against yet the brg is there plain as day. So am I missing something here and if not what is the magic that is stopping the oil from leaking out of here?

My next step was going to be to remove the output shaft housing to replace the reverse selector seal, yoke seal and that was going to be about it. Is there any point in taking the transmission apart further? It shifted fine, no noises and the gears all look good so far. Is there a easy way to check the syncro rings for wear without taking them out and looking at them?

Thanks.

[Domenic T.]

Re: 67 M20 input shaft seal?

Greg,
1967 did not have a seal and was not machined for one. Just remember not to fill it to the top of the fill hole. It was supposed to be 1/2'' from the top when cold and I have heard that that was to high by another with lots of munci experiance.
The trans breaths out of the hole in that housing and when you stop a oil slinger keeps the oil from leaking.
Over filling was a comon cause of leaks.
I would not take it apart any further. Actually the tail housing can stay on to change the 2 seals. It's easier than it looks.
Also clean the cluster shaft in the front of the trans and put a sealer on the area just as you install it as it is another source of an oil leak.

DOM

[Wayne M.]

Re: 67 M20 input shaft seal?

....I pull the side cover off and except for very fine bronze looking particles in the oil(which I assume is normal...right?), it all looks good. Then I take off the brg retainer for the input shaft to replace that seal and....there is no seal...?? There isn't even a machined surface on the shaft for a seal to seal against yet the brg is there plain as day. So am I missing something here and if not what is the magic that is stopping the oil from leaking out of here? ......

Hi Greg -- going to the B.C. chapter meet this weekend, in Vancouver ?
Check this DB link to a similar question; I think this'll answer the part about the input shaft/gear lack of seal (in the sense of one you're expecting to find). Much how Dom has explained it.

https://www.forums.ncrs.org/showthre...73913&uid=9999

[Joe L.]

Re: 67 M20 input shaft seal?

This is my first time ever working on a Muncie so please bear with me.

While changing the clutch on my brother's 67 Camaro I figured that I would try and stop some of the leaks which look to be mostly coming from the shifter shaft seals but I figured that I might as well change all the seals since it was out. So I pulled out my 69 service and overhaul chassis manuals and started to take things apart.

I pull the side cover off and except for very fine bronze looking particles in the oil(which I assume is normal...right?), it all looks good. Then I take off the brg retainer for the input shaft to replace that seal and....there is no seal...?? There isn't even a machined surface on the shaft for a seal to seal against yet the brg is there plain as day. So am I missing something here and if not what is the magic that is stopping the oil from leaking out of here?

My next step was going to be to remove the output shaft housing to replace the reverse selector seal, yoke seal and that was going to be about it. Is there any point in taking the transmission apart further? It shifted fine, no noises and the gears all look good so far. Is there a easy way to check the syncro rings for wear without taking them out and looking at them?

Thanks.

Greg------


You don't have to disassemble the transmission to check the synchro rings and gears. You can do it just by removing the side cover. Of course, you can't check for subtle cracks in the rings, but you can check the teeth as well as the engaging teeth on the gears. What you want to see is sharp pointed teeth on each. You don't want to see any broken-off teeth or teeth with greatly rounded points.

It never ceases to amaze me when I see guys looking at the innards of transmissions at swap meets, they all focus on the primary teeth on the gears. Those are almost always OK, particularly since the gears are constant mesh (except reverse). What one needs to look for is the condition of the small synchro-engaging teeth. That's where the problems usually lie.

[Wayne M.]

Re: 67 M20 input shaft seal?

..... but you can check the teeth as well as the engaging teeth on the gears. What you want to see is sharp pointed teeth on each. You don't want to see any broken-off teeth or teeth with greatly rounded points. ..... What one needs to look for is the condition of the small synchro-engaging teeth. That's where the problems usually lie.

Greg -- here's a few pics; an M22 first gear (some of corners of the engagement teeth are slightly rounded but not bad, IMHO), and the two variations of syncro gears -- both NOS. Your brother's '67 will probably have the 2nd design (3rd pic), which has more brass (bronze ?) in the shoulder -- less prone to breaking.

.

[Greg L.]

Re: 67 M20 input shaft seal?

Well I managed to get her all sealed up and the syncro rings and gears look nice so it should be good for a while now. I didn't know about keeping the fluid level a 1/2" or more below the fill hole so I'm glad that was mentioned or we would have had a oil leak for sure!

Thanks for those pics too Wayne. They really helped to give me an idea of whether these were okay or not and to compare them to new ones. I'm sorry to say that I won't be able to make it to Grant's on Saturday. I was planning for it all summer but it's just not going to work out at all. I hope you have a good time.

[Ronald L.]

Re: 67 M20 input shaft seal?

Where does one buy a synchro for a 66 67 Muncie these days?

[Patrick N.]

Re: 67 M20 input shaft seal?

Where does one buy a synchro for a 66 67 Muncie these days?

Rebuilt my completely blown M20 and sourced my parts from www.riversidegear.com

Others may have more recommendations.

Pat

[Ronald L.]

Re: 67 M20 input shaft seal?

Pat, thanks much. Turns out a friend who races F-150's uses this shop, and it is in-state.

[Patrick N.]

Re: 67 M20 input shaft seal?

Ron, glad to help out. RSG was the right palce for me. The only thing undamaged on my transmission was the case itself-how lucky! The rest was shrapnel from the previous owner. It was the day he parked the car 20+ years ago

[Ronald L.]

Re: 67 M20 input shaft seal?

Pat,

Mine is not that bad, I can feel a less that perfect synchro on down shifts. This will be a good winter project while we are in the snowbank; thus timely to line up parts, drop it & head off a problem and fix the rear seal too. That being almost as bad as the drip from the original oil cannister.

[Joe L.]

Re: 67 M20 input shaft seal?

Where does one buy a synchro for a 66 67 Muncie these days?

Ronald-----


There's no problem, at all, in obtaining synchro rings for a Muncie. They are available from numerous sources. The caution here is that I have heard from several folks that the aftermarket replacement synchro rings do not seem to work as well as the original ones. In fact, even the later GM synchro rings of supercessive part number, were, apparently, not as good as the original ones. I expect that the later GM rings, which are also no longer available, are probably the same piece that's offerred in the aftermarket today.

By the way, not only are the synchro rings for Muncie transmissions available, but so are all other parts, including some that were never available from GM (like a WIDE RATIO M-22 gear-set). All the internal parts are manufactured by Masiero S. A., an Italian company that's one of the, if not the, largest manufacturers of gears in the world. The case, side cover, rear bearing plate and extension housing are manufactured by Autogear. The Autogear pieces are not configured exactly like the originals but, functionally, they are FAR superior.

[Patrick N.]

Re: 67 M20 input shaft seal?

The case, side cover, rear bearing plate and extension housing are manufactured by Autogear. The Autogear pieces are not configured exactly like the originals but, functionally, they are FAR superior.[/quote]

Intersting, Riversidegear offers most every part / cases from Auto Gear as well. Not sure what buying direct from GM dealer prices are like but RSG is reasonable.

[Joe L.]

Re: 67 M20 input shaft seal?

The case, side cover, rear bearing plate and extension housing are manufactured by Autogear. The Autogear pieces are not configured exactly like the originals but, functionally, they are FAR superior.

Intersting, Riversidegear offers most every part / cases from Auto Gear as well. Not sure what buying direct from GM dealer prices are like but RSG is reasonable.[/quote]


Patrick------


If you mean buying Muncie parts from GM, forget it. Virtually all Muncie parts, except for a few small parts and the front bearing retainer, are long-since discontinued.