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I rebuilt Porsche 5 speed transmissions back in the 70's but am unsure about this muncie. Look at the photo.. the synchronizers are shot, I know a rebuild is warranted but I wonder about 2nd and 3rd engagement teeth on the gears. They look quite short to me suggesting I should replace them but I wonder if I do replace them with new gears, do I need to replace the opposing gears on the intermediate shaft, too.
back in my day I was always concerned when replacing gears that if spacing was changed gears would whine ( I would take caliper readings everywhere and duplicate those measurements, new gears and bearings could measure slightly different then old ones)and also.. opposing gears needed to be replaced as well. gears whining was the punishment for error. Maybe Muncies are more forgiving then Porsche 5 speeds?? anybody know.
and does anyone believe the wear on 2 and 3 would cause those gears to pop out? maybe I should not replace the gears!!
The pictures aren't great, but it looks like the 'points' are worn and blunt, no longer sharp and crisp. You should PM DZAuto (Tom Parsons) on this forum, or hope he chimes in. He is 'The Man' when it comes to Muncie transmissions...(along with just about everything else!)
The "opposing" gears are the countershaft which has fixed gears on it - would have to replace the whole countershaft which probably wouldn't normally be done unless worn or chipped or missing teeth are present (absent?). Good news is there are excellent Italian made gears and complete gear sets available that are imported by AutoGear. I wouldn't worry about prospects of gear whine. If any it would probably be in the lower gears. Once it's locked in fourth it's direct drive. But yeah - DZAUTO (Tom) is the go to guy on Muncies.
another question.. My car is a 64 (Feb, 64) which calls for a 3851325 casting or earlier. It has the small cluster. What are your guys thoughts on buying and repairing an early one. Everything else in the car is matching.. I felt the newer unit is a superior unit so I felt comfortable using it but now I see it needs gears I wonder if I should trade it off for a correct one. There is a guy locally that has many m20's and is will to trade me for very little money. His would likely need to be rebuilt.
I would definitely avoid the Ebay gears. There are high quality gears available and for the small price difference why go cheap. The Italian gears are beautifully machined. Larry at D and L Transmission around Chicago, and Paul at 5Speeds are AutoGear authorized dealers and sell the good gears and anything else you may need. There are other suppliers in addition to them that others may recommend.
Avoid the China parts.
Unless you want "numbers" the 1" shaft is more rugged than the 64.
Personally, I don't want or like the locking sliders. They don't feel right.
You have serious wear, but until it is disassembled, you won't really know.
You may or may not see wear on the id of the cluster gear. Unless you find chipped or broken teeth on the cluster, the tooth pattern will likely pass.
Good gears and parts may seem expensive, but relatively so they really aren't.
Dan’s list of reputable builders is spot on. Keep your purchases restricted to that group; otherwise, you are asking for problems.
Muncies are easy to rebuild and, relatively, inexpensive. If you decide to purchase new gears make sure you purchase new synchro hubs, as well. Tear it down once and do it right the first time.
I agree.. the extra view bucks are worth the confidence of knowing its right.
I expect I will replace 2 and 3, and put in new bearings, seals and synchronizers. The only concern is the opposing gears not being replaced.. I'll probably take a chance but double check the new gear thickness's so to keep all gears wearing against the same surfaces as before.
I read a disturbing fact about the muncies.. they have no seal up front therefore always leak a little. How crude.. the technology was there always back to the 30's. I hated that those 60's cars always had a drip, my Volvo's never drip even with 150000 miles.
I rebuilt Porsche 5 speed transmissions back in the 70's but am unsure about this muncie. Look at the photo.. the synchronizers are shot, I know a rebuild is warranted but I wonder about 2nd and 3rd engagement teeth on the gears. They look quite short to me suggesting I should replace them but I wonder if I do replace them with new gears, do I need to replace the opposing gears on the intermediate shaft, too.
back in my day I was always concerned when replacing gears that if spacing was changed gears would whine ( I would take caliper readings everywhere and duplicate those measurements, new gears and bearings could measure slightly different then old ones)and also.. opposing gears needed to be replaced as well. gears whining was the punishment for error. Maybe Muncies are more forgiving then Porsche 5 speeds?? anybody know.
and does anyone believe the wear on 2 and 3 would cause those gears to pop out? maybe I should not replace the gears!!
Hi, here is a link to Paul G. lots of videos on the top by one of the best around at rebuilding Trannys
and does anyone believe the wear on 2 and 3 would cause those gears to pop out? maybe I should not replace the gears!!
I overlooked this comment earlier - and I'm no transmission expert but I don't believe that gear tooth mesh on these transmissions is a typical cause for kicking out of gears. I believe that is more typical of worn slider engagement teeth on the gear, wear of the syncro slider itself, improper shifter adjustment, side plate and fork wear and also a really worn input or input bushing is said to be common.
Someone please correct me if I'm wrong.
I think a new gear meshing with an old gear will at most create additional backlash and cause you some gear whine or moan.
Worn brass blocker rings will create engagement difficulty, gear clashing and so forth.
If you are really in the mood to do this right and one time only, give Larry or Paul a call and price out a complete new gear set with new sncros/sliders. I rebuilt my M20 last year with a new AutoGear Super Case, new Italian wide ratio, M22 coarse angle gears and other internals/small parts. Larry suggested reusing my sideplate (new forks), tailhousing. The other retained parts were the main shaft and reverse gear/idler. I would have to go back and look but I think the whole parts list was around $1200 to $1300. Reuse your main case if in good condition and you can probably knock another $250 - $300 off of that.
I doubt you need to go to this level to get a sound transmission out of your rebuilt, but it is an option if you want the piece of mind. Providing your own labor it's not too bad overall in cost.
Here are some of the new gears
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Super Case
New assembly
Last edited by DansYellow66; May 25, 2018 at 12:53 PM.
the video was very informative and putting in new italian gears I may do. I'll think about it over the long weekend. I have a tendency to put as little money in as possible but I may put in more. I wish it was the correct trans for the car, then I would just do it.
One more post before someone far more knowledgeable than me kicks me out - if you are rebuilding yourself I would be sure and get a really good set of HD c-clip pliers like this.
And the only big issue I had was removing the pin that secures the reverse fork in the tailhousing. It's tapered and has to be driven out from the bottom to the top. It's easy to mangle it up in the process and in full disclosure, by the time I got mine out I just went and got a nicer, used tail housing from Larry for minimal cost. It pays to take precautions with it. Possibly centerpunching it first as once you start pounding on it with a punch, the pin is soft enough that it and the case just all mush into one divot and then it's easy to get off the mark.
And dropping the main cluster in to clear the countershaft and get it fully to the front is almost more of an art than trick - but it goes with a little patience. The videos should deal with this pretty well.
I have good c clip pliers.. Thanks for the tips. I haven't decided yet. It's possible I could find a good rebuilt one thats not so much more then parts and be the correct casting.
its a pleasure to be past all that fiberglass work that is so exacting.
I agree.. the extra view bucks are worth the confidence of knowing its right.
I expect I will replace 2 and 3, and put in new bearings, seals and synchronizers. The only concern is the opposing gears not being replaced.. I'll probably take a chance but double check the new gear thickness's so to keep all gears wearing against the same surfaces as before.
I read a disturbing fact about the muncies.. they have no seal up front therefore always leak a little. How crude.. the technology was there always back to the 30's. I hated that those 60's cars always had a drip, my Volvo's never drip even with 150000 miles.
I think you may be referring to the counter pin that holds the cluster in place. After numerous removals, the case needs to be bushed; otherwise, a leak will develop. I don't think you are referring to the retaining cover, which does have a gasket.
Don't know if this helps in anyway but it's from the 1966 chitons rates and parts manual I found going through stuff in the garage. I was going to get rid of it but I may keep it for the breakdown pictures. It's also fun to look at the prices.
this unit has a peened closed opening for the intermediate shaft and the forks are well worn under specs. Its been really messed with. I spoke to D & L which was very helpful. It will take many parts and machine work to make it great, less parts to make it satisfactory. I want to first see if I can find a decent early 64 that will match my car. My car manf date is very early January 1964. I believe that would mean the correct casing # should be 3851325.. can anyone confirm and lead me to a photo including a date code. tailhousing # 3846429 and sidecover 3831707.
it should have a rounded upper extension housing bolt boss. Now what does this look like, I feel like a young pup, anyone have a photo. My local guy says his floor is covered in m20s.. maybe I get lucky.
Here is a comparison of a rounded and square boss on the top, rear of the main case.
Cases up through mid-65 had the rounded boss, then after mid-65 they were all square. Thus, ALLLLLLLLLLL 63-64 main cases had the round boss.
It's your money, and your car, so you can do as you wish. BUUUUUUUUUUUUT, if it were mine, and a dated 64 case was located, I would have the case bored for the larger (66-74) cluster gear shaft. This simple modification will make a 63-65 case (all had the smaller 7/8in shaft) more durable and eliminate the leak which frequently develops around the shaft hole at the front of the case. Then a 66-later input and cluster gear can be installed. OR, if you want to go up one more step, an M22W gear set can be installed to add a little more strength as well as produce that distinctive M22 whine (a feature that I like very much).
And one final comment.
There are other good sources for Muncie parts (and T-10 parts), but I've been buying my 4sp parts from Larry Fischer (D & L Transmission) for over 30yrs and I assure you, thee is no one more knowledgeable or better to deal with.
any expert m20 rebuilders out there
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