Just got the transmission onto my bench. I did a bit of cleaning yesterday and that is it.

As for as I know, it may never have been apart or even out of the car. I was going to just put it back in my car with a new clutch but got to thinking "since I have gone this far", "while I am here".... you know how it goes.

So the clutch needed to be renewed but the car shifted fine and stayed in all gears. The problem was that the shifter was sloppy as all hell. My friend has a 64 with an M20. I drove his and the transmission was very tight and that is when I realized that mine needed some work.

I know absolutely nothing about transmissions other than the 5-10 or so hours I have now watched on youtube. So I may take a leap of faith and rebuild this myself.

So my question is, is the sloppiness that I refer to normally the shifter linkage bars etc, the sliders and the syncros or what?

How do I make this thing feel like a new transmission.

I was reading about the sliders and forks possible being a big part of the transmission with sloppiness.

Asking for help where to begin.

Thanks, Pete

 

IMHO, I would not rebuild the Muncie unless it is popping out of gear, gear oil looks bad or has lots of metal particles or grinds or makes noise.

Here is the "go to" book if you decide to rebuild:

Muncie 4-Speed Transmissions: How to Rebuild & Modify (Sa Design) Paperback – October 21, 2014
by Paul Cangialosi (Author)

If you have the factory tee shifter, I would suggest you first rebuild the shifter mechanism/arms with a rebuild kit from one of the Corvette vendors and adjust the shifter arms per the OEM procedure and see what you think. My experience is doing this will take a lot of slop out of a worn OEM shifter mechanism.

Here is link to one vendor, they all supply something similar.

https://www.zip-corvette.com/69-76-4...build-kit.html

Hope this helps.

 

Why do you say don't rebuild it? is it just the level of complication of the job?

Is it likely that the shifter rebuild will take out much of the slop? I do have the original t handle that has never been touched to my knowledge.

Shall I at least take out the oil and check that. Someone said I would be crazy to not replace the back yoke and bushing and open it up to see how the gears look since it is out of the car.

Last thing i need is a leak after this large job.

Does anyone know how many hours a newbie might take and the inherent risks if a newbie tackles a rebuild on the M21?

 

Just my opinion, I am trying to get to the point of "if it is not broke, don't fix it." unless you have indications of problems. Muncie's I think are pretty robust. Your call, I am sure you can do the job if you read Paul's book.

My experience is the shifter rebuild kit got me a lot of benefit with reducing slop and is the easier first step.

While you have the Muncie out, I would replace the rear seal and the cover seals for the arms.

 

My luck would be that if I didn’t rebuild it, as soon as I put it back in the car it would fail lol! While you have it on the bench, I would definitely pop the side cover and check it out. Post the pics here and the experts will tell you what it looks like. Synchro’s and forks and such. Would definitely get the old oil out and give it the once over. I agree also that a sloppy shifter will give you the feeling you describe. Paul’s book is a great resource. Good luck!

 

if it goes into gear and stays in gear then you should be fine. You can pull the side cover and inspect it to clear your mind of questions. The forks will give you slop and the bushings in the shifter it self will too. If your shift rods are in the upper holes in arms, you are in the long travel mode and that may make you think there is slop. The gears and internals will not produce slop.

I just bought a used one that was pulled for a 5 speed swap and was told by the mechanic it felt pretty good. But he only drove it a few miles. Apon inspection the engagement teeth were wearing slightly and reverse was really bad.

It turned into a complete rebuild just because I was in there and didnt want to replace one thing and not another because I drive my car pretty hard. If you just cruis e and dont grab gears like a maniac you will be fine. I ended up replacing everything except the slave gears and the front and rear housings. Its just how my mind works but I didnt want to pull it out for a leak or something which was why I had to pull my motor the second time this winter. (total of 4 times so far).

The big thing I came across was that you dont want to use the gl5 synthetic gear oils. It doesnt stick to the gears long enough to get pulled to the top of the case. Its too slick which is bad without an oil pump.

I would pull the side cover, check the fork arms for wear, they will give you a little slop as they will have to travel a bit more to take up the wear to push the sliders.

you can see all the teeth so you can slowly spin the gears to see if there are any missing or if they are chewed up

Defintley wiggle the yoke and check for slop. you may not have to replace the yoke, just the bushing. replace the rear seal and any others that are leaking.

You can see the leading edge of the reverse gear was ground up an d missing chunks . You definitly want to be at a full stop and put it in first , then reverse to synch up
the teeth.

Do you have a press, it makes pulling the speedo gear off a breeze?

If you do rebuild it, it isnt rocket science. Buy Pauls book and watch the various videos he has for tips. My gears came in great shape and had the burrs all filed off when they arrived. I just had to put it together. I did buy the sealed front and rear bearing assemblies so I wouldnt have to mess with the needle bearings. I had to do a little fitting with the case spacer to get it to fit.

I didnt buy matched sets for the sliders and syncros, I think they were out or something but luckily there wasnt alot of slop in the synchros

I can post pics of the teeth if yo need some reference pics, i kept them in a box and save the forth gear to line up the clutch teeth, its a lot better than the plastic tool

 

Remember to put it in second to pull the side cover, if you dont the fork will come off in the tranny, which isnt a problem but then you have to figure out how to put it back together.

Looking at the gears, you can see that all the gears except for reverse are always spinning, its the syncros and the little engagemment teeth right nest to them that wear the most. There just isnt any room in there for slop unless the bearings let go and then thats a whole other problem. If you do pull the gears from the case you may want to check the magnet on the bottom, mine popped of with a stab of a screw driver. I ended up tapping it for a magnetic drain plug. If you dont have pipe thread taps and the propper ream, have a shop do it.



I got this off the web, it shows 2nd gear engaged. You can see there isnt anything that can give you slop and you cant over shift past a gear. its either in gear or not

 

Heres a video that shows how 4 speeds work, jump to the 2:05 mark. it makes visualizing whats going on easier to understand and helps when you put the tranny together

https://www.bing.com/videos/search?q...F&&FORM=VRDGAR

 

Thanks so much, 20Mercury/69ttop502 and Rescue


I kind of enjoy the process so rather than take it to the shop, I will do a little investigation first.
I will make sure it is in second gear and open up the case and check out the oil, and have a look at the gears etc. and sliders and fork.

Rescue, those pics are very helpful. I will try to get the case off today if I can find a few hours of time and post a few pics.

It sounds from what everyone is saying that much of the "slop" is not coming from inside the transmission. I will dig out my shifter which is packed away some place in a bin. Sound like it may be the culprit to a certain extent.

Pete

 

Actually most Muncie DO have quite a bit of slop due to age. You can feel it in the total backlash between the input and output shafts. The high end shops will actually bore and offset bush the counter pin bore .005" closer to the main shaft line to clean up some of the backlash.

BUT - a factory shifter is usually sloppy as heck - some can be the mechanism and some can be worn holes and shifter rod linkage ends. Nothing feels like a Hurst...

 

There are a few great videos on 5speeds.com. He shows you how to rebuild a Muncie with shop tools. It easier if you have a press but these videos are good. I have rebuilt a stock shifter a couple times. Yes, you will get less slop but it still ain't great. I finally had to go to a Hurst.

 

How long it would take to replace all the seals at home with the proper tooling?

Any chance on doing that with the trans on the car?

 

theres not enough room. For paper gaskets,you have a gasket on the front , 1 on the side and 2 for the middle plate/tail housing . The speedo has an o ring, the 3 shifter levers have seals plus the large main seal for the yoke.

Can you determine if you have any leaks? to replace the middle plate seals you'll have to pull the main shaft out of the case. I doubt the big paper seals are leaking. most likely all the ones that have rubber may have dried out. You definitley need the side plate gasket to check your gears and the shift yokes. You can replace those seals while your there. I think you can replace the reverse shifter seal form the outside, I dont really remember. The speedo plug you can just pull out after you remove the little bolt and twist the retainer plate/ washer

 

What were the shifter linkages like when you pulled the box. Just pulled the motor and M21 out of my car and had found some of the nuts backing off the linkages what was the loose feeling was that had crept into the shift.

 

So I have the inspection cover off and couple of things of note. I now see how the slop could and likely is mainly the actual shifter and not the transmission. And as you say azza, I do recall some of the bolts not being all that tight when I removed the shifter. That actual shifter "tabs" on the cover which attach to the forks are actually very tight when shifting by hand on the bench. I do notice that the upper holes are much bigger than the lower set of holes on the tabs. Is it correct that I can move to the lower holes so I have a shifter that doesn't move quite as far? My first gear was hitting the console cover. The holes are meant to be the same size are they not?

Anyway, here are a couple of pictures of the inside if anyone has any comments. I did notice in the yellow circled area of the internals what I thought was teeth removed off the "hub" but after watching Pauls videos, I am starting to think that they are not teeth wiped out but are rather supposed to be like that.

Any comments on the state of the transmission gearing/syncros etc would be very much appreciated. One of Pauls videos suggested to put the back end of a 3/8 inch drill into the slider where the fork sits to determine wear. Mine was very tight so I am starting to think that someone has been into this transmission at some point.

Is there any other tests I can accomplish to help determine whether or not I should pull this thing completely apart?

 

The yellow circle in the Last pick is of the slider. It's still in second gear, you can pull or push the slider back towards first. Second gear is usually the most worn from hotrodding off the lights. Compare the teeth of them all to each other for wear. The gold teeth are the synchros,

you can then slide it back to get it back together. I have picks of worn yoke arms I can show you. Yours look okay, can you use a flash to get better pics

The shift arms should be a tight fit. The big holes on the top might have been opened up for bushings. The lower holes shorten the throw dramatically. My shifter is almost touching in reverse but not close now in 1st and 3rd.

You will have to adjust the neutral setting when you go from the upper to lower. My front shifter was almost 1/4 inch further out.

I have picks of rebuilding my shifter as well I can post a thread. Super easy

 

Thanks Rescue,
I was lucky enough to have lunch today with a fellow who has been through lots of these muncie's. His word was that it looked to be a pretty good transmission but should have some work on the hub/syncro and perhaps slider for forth gear and also that the forks which i thought looked OK are perhaps not. He said definitely replace the yoke at the tail of the transmission.

So I just need to decide if I will tackle it myself.

I will definitely take a crack at rebuilding the shifter myself. Today I started cleaning the shifter up. But I don't really understand what can be rebuilt because I really don't see any bushings that can be replaced? I would really appreciate a few pictures of the rebuilt of that if you have them. Short of wire wheeling and perhaps a repaint, I am not really sure what else to do. I will definitely go to the lower holes for a shorter shift and then readjust the neutral point. (I did that after I just got the car when I could not get it out of gear)!

 

The shifter is most of your slop. Vendors have rebuild kits like this one:



You do need to make the alignment tool so you can rebuild it and set the shifter rods to the proper length. It looks like this:





I'd set it up for short throw action as you transmission levers have the lower holes. Makes a world of difference IMO. When you install the shifter put the alignment tool in it then adjust the shifter rod ends to the lower holes. Even if you don't decide to go short throw you still need to use the alignment tool to make sure your shifter rods are adjusted to the proper length.

The lower holes in your yellow circles are for short throw action:

 

If you are going to go to the trouble of rebuilding it, consider Syracuse gears or replacement parts. Because of the damage in mine, I realized it was only about $350 more so I bought the whole transmission and assemble it myself. They have a number of options and gear ratios. I changed gearing (went to a 3.08 rear with a 3.00 First gear) to match the way it will be driven.

My numbers matching box now sits on the shelf. From a cost standpoint, I can probably sell the old trans for more than the difference. (At least that is what I told my wife)

 

Sorry, I don't know the terminology, but I will describe the parts.

I rebuilt the linkage about 6 months ago. There was a fair amount of wear on the two step pin supplied with the rebuild kit but there was also wear in the holes of the shifter plates this pin fits through. I probably should reamed the holes back to round and had a new pin machined... but I didn't. The piece that blocks you from catching two gears and looks like the bottom of a rocking horse is thicker in the rebuild kit and crutches this wear by removing side to side play but you still have a vertical looseness.

On mine, The cradle (looks like the bottom of a rocking horse with both rockers) that holds the shifter plates was bent and twisted. I bent this back so that the holes were square and aligned side to side.

The stack up dimensions of the shifter plates and the shift blocker were .030 less than the space between the the inside of the cradle but when assembled they were tight probably due to the surfaces not being machined. I could not find any tolerance to hold so since it was tight, I left it.

The U that goes over the cradle was an slight interference so I assume that is good enough but I think I will make spacers that fit over the two stepped pin. I'll keep them about .005" less than the space between the bolt head and the U on one side and the support and the U on the other. This will eliminate the need for the C clip and prevent any deflection.

Finally, my shift shaft is loose in the shifter block. In other words, the round part that you move is loose in the square part with tang that moves the shifter plates. I have two shifters and both are loose so I assume yours is going to be too. I may try to weld this.

With all that, I still have about 1/4" of movement in both directions at the ball. The side to side slop is the size difference between the shifter tab and width of the shifter plates. The front to back is the gap between the inverted U and the block on the shifter handle where the shifter pivot pin is inserted. This space is about .020. I could shim that, but am concerned that the shifter movement would tear up the shim.

Hope this helps somebody.