Hi all-
I have an original numbers matching M21 for my L-36. I took it in to a shop that specializes in older muscle cars and was told upon inspection that it looks as though there is nothing to indicate it is not properly functioning, but 2nd and 3rd gear look worn, worn forks, synchros. 1st, 4th, and revers look fine as well as counter shaft. To clean and rebuild with the new parts and seals, the labor is around $450; with all these new parts (Italian made gears), the cost is $1800. Are parts really this much now? The unit shifts great, never pops out of gear, and no significant leaks that I can detect with 123,000 miles on it. Any thoughts?

 

pull the trans out keep it if original to car then buy a new auto gear N23. Around $2300.00 it's a world's stronger version of an m22 trans.

 

Thanks for the response, but I'd like to keep this unit in the car. I just don't want to pay way more than necessary to freshen it up. Looking at the price of Italian gear sets just for an idea, the whole set runs for about $800. I would think that a more reasonable cost might be closer to $1,000 to $1,200 but was hoping to see if someone could chime in about the repair cost.

 

You can go to Paul Cs website and get parts costs there. You can ask him for a repair estimate as well. He would do a much better job. Ask your repair guys if they custom pick the synchros for each synchro hub. Did they say the reverse synchros look good?

There are no reverse synchros.
https://www.thegearbox.org/Muncie.html
https://m.youtube.com/c/GearBoxVideo/playlists

 

Thanks RR,
I messaged Paul through his website since I don't think he's a member here. Hopefully he has some insight as to whether or not this price tag is extreme or not.
I may even just rebuild it myself down the road if the cost is really that high; it seems as though people think with Paul's book/video that it's pretty do-able with some common sense and work ethic. I'd love to hear other's opinions as well, especially since there were not any shifting issues (at least for the last 50,000 miles since I had the car).

 

diy for sure.. ihave never rebuilt one. Tools and parts are a fraction of what you were quoted..and i have a new press and tools.
paul at 5speeds.com for parts and advice..
videos excellent
here ya go
https://www.corvetteforum.com/forums...r-etc-diy.html

 

Agree with interpon.

I rebuilt my 68 Muncie M20 this past spring and I thought it was pretty straightforward and fun, not like some other C3 jobs, LOL's!

I bought Paul's kit
Muncie Rebuild Kit For Years 1966-1974 (5speeds.com)
Checked out some others kit and Paul's has the best components, bearings, ect.

You need the regular tools and I used my 20t HF press and not much more. There is a special thin metal wrench you need to get the end nut off.

Suggest you consider doing yourself if you like to wrench. Paul's videos U tubes are great plus buy his book.

I would be surprised if your 2/3 gears are worn out. My reverse gears were chipped (more common since the reverse gears have no synchros) and I bought a used set from a guy that bought out a going out of business Corvette's shop Muncie parts. PM me if you want to contact him and buy some used gears. He has rebuilt Muncies for a longtime for a side business.

New Italian gears are very expensive, buying used gears is a better way to go or buy a used Muncie and remove the internals to install in your original case.

So, having said all of that and I am trying to get to the point in life where maybe you do not fix it if it is not broken, if your Muncie works good, and you likely do not run up thousands of miles every year, you might just run it. Paul's book I think has some insights on what to look for as for gauging wear.

My 2 cents and hope this helps.

 

Thanks for the replies so far. I would have rather had a specialist do any work, but the price tag just seems too high for the parts. I don't mind spending the $450 on labor if I don't do it myself, but since it's shifting ok, I may just have the shop clean it, put new seals in, and run it until I notice any issues- then probably tackle it myself. I heard a press is not necessary but nice to have for the work, although I have always wanted to have one in my garage. I don't take it to any strips and I'm pretty easy on it when I drive, save for occasional punches for s's and g's.

 

I rebuilt mine and you would benefit from the press to get the speedometer gear off the main shaft. I think that was the only instance. You could take it to a machine shop to have that done. I think I heated the gear and put the shaft in the freezer to get her back together. Watching Pauls videos and grabbing the book is all the experience you need as long as you know a flat head from a Cresent you will do fine

 

Agree, and never turn down an opportunity to buy another tool I still have tools I use from paper route money from '65.

Thought for you, suggest you buy Paul's excellent book


How To Build and Modify Muncie 4 Speed Transmissions Book (5speeds.com)

And then study a bit and then decide what to do.

(Sure a BFH might get it done, but the press is so much slicker and easier and less likely to damage stuff.)

 

You can drop the mainshaft on a thick piece of wood from your belt height if you don't have access to a press. The gears will come off that way but it is obviously a "Bubba" technique. I did that before I had a press.

I would not mix new and used gears in a pair unless you are broke. Same for third party used gears. You can end up with gear noise that way. They will work, but you might not want to accept the risk of a noisy gearbox.

A gearbox overhaul is always a box full of judgment calls. Some parts are always good to replace such as needle bearings, thrust washers, seals, ball bearings, roller bearings, brass synchro rings. Some are harder to decide - gears, sliders, forks and others. The reverse gear ALWAYS looks bad BUT..... you never go full throttle in reverse.....so, they are not really a "must replace" item.

LOTS of decisions.