Opinion on 70 Muncie Gears

[Stephen B.]

I would like some opinions on the wear on the gears and the gears' points that work with the syncho rings. Of course, I plan on replacing the syncho rings. 4th gear and the counter gear already have to be replaced because of breakage. I am toying with replacing all of the gears.

These are 2nd, 3rd and 4th gears.

Thanks in advance.

[Joe L.]

Re: Opinion on 70 Muncie Gears

Stephen-------


I've seen a lot worse than these remain in service. However, sometimes when one combines new brass synchros with "somewhat less than new" synchro teeth on the gears, shifting problems, usually minor, are the result. You can't go wrong with new gears.

Sometimes, folks attempt to "sharpen" worn gear synchro teeth by grinding. However, this is a short-lived solution. The teeth are case hardened. Once the case hardening is gone, either through wear or grinding to sharpen, further wear will occur rapidly.

[Jack H.]

Re: Opinion on 70 Muncie Gears

In the top picture...those dimple marks on the synchro cone riding surface along with what appears to be some scoring/heat coloration would be interesting to investigate further. Maybe it's just the picture?

Is it something you can feel?

In general, I agree with Joe in that I've been surprised at how bad some gears seem to look, but still function adequately.

[Domenic T.]

Re: Opinion on 70 Muncie Gears

I agree with Joe and Jack. We called those dog houses and the sharper the better. Most don't realize that that is what grinds when missing a shift. When they get really bad they will cause the trans to jump out of gear when you let off the gas. I would say that they went thru 1/2 of their abuse range.

Dom

[Edward J.]

Re: Opinion on 70 Muncie Gears

Steve, this is a job you'll only want to do once, mixing and matching gears can sometimes cause gear whines and noise. If you can find NOS gears, than you can mix. most of the NOS trans gears are far and few between. there are some guys in the driveline that maybe be able to help source what you need for the rebuild.

[Stephen B.]

Re: Opinion on 70 Muncie Gears

I appreciate everyone's input on the subject. I plan on just replacing the complete gear set and counter shaft. This transmission has over 200,000 miles on it anyway. lol.

[Gary R.]

Re: Opinion on 70 Muncie Gears

With that amount of miles I would check the case countershaft holes, you might need to bush the front one.

[Stephen B.]

Re: Opinion on 70 Muncie Gears

That's a good idea. The bores appear to be tight and in good shape.

[Gary R.]

Re: Opinion on 70 Muncie Gears

I would also weigh the value of rebuilding that trans vs buying a complete new super case M-20. If it was me and I planned on driving a lot I would look at storing the original and going with a new auto gear trans. They are stronger and have worked out the kinks the original Muncies had.

If you are not paying for labor to rebuild it then it would be more efficient to rebuild it, if you are paying labor then it could be more reasonable.

Good luck. I have used the new gear sets and new individual gears and the only issue I had was with a rev idler in a 69 M22. The new ilder caused the trans to bind up, I installed the original and it was fine and worked without issue.