Muncie M20 - 3rd gear synchro problem.
Thread Starter
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
Muncie M20 - 3rd gear synchro problem.
I'm having a problem on my yellow '68 Vert with the 3rd gear synchro. Shifting up is not a problem but when downshifting, I have to shift first from 4 to 2 and then from 2 to 3 to get the transmission into 3rd gear.. It has been like this for a while and doesn't bother me as I'm used to it, but I'm thinking in selling the car and want to get the tranny fixed.. I also need a new clutch, so the tranny has to come out anyways. Can the 3rd gear synchro be fixed without a full rebuild of the transmission? (the transmission works great otherwise)???
How much am I looking at for the cost of having the transmission fixed or is this something that I can do myself (fixing the 3rd gear synchro)?
How much am I looking at for the cost of having the transmission fixed or is this something that I can do myself (fixing the 3rd gear synchro)?
Thread Starter
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
I think that I'll get a better price by MORE than what it costs me to have the transmission rebuilt. As I'll pull and re-install the transmission myself, it will only cost me the price of the rebuild.. I have no idea on what a rebuild will cost.. I can buy rebuilt M20's for about $650 - $750, so, if it's more expensive than that, I'll just get another one and sell mine on Ebay.. It's not the matching transmission (with the VIN number stampted on it) anyways, so it won't matter.
Race Director
Joined: May 2006
Posts: 18,734
Likes: 2,582
well this is a rebuild kit so if you can do it yourself...........
http://www.ecklerscorvette.com/corve...1965-1975.html
http://www.ecklerscorvette.com/corve...1965-1975.html
Melting Slicks
Joined: Sep 2004
Posts: 2,655
Likes: 19
You can rebuild it yourself. Instructions/manuals are available online or you can buy on ebay. The only tools you need besides wrenches etc.. are a press, a piece of 2" pipe, and buy a front input nut wrench.
I've bought a few kits from these guys.
http://www.tbtrans.com/muncie_4_speed.htm
I've bought a few kits from these guys.
http://www.tbtrans.com/muncie_4_speed.htm
Thread Starter
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
well this is a rebuild kit so if you can do it yourself...........
http://www.ecklerscorvette.com/corve...1965-1975.html
http://www.ecklerscorvette.com/corve...1965-1975.html
Drifting
Joined: Aug 2010
Posts: 1,626
Likes: 140
From: Kanuckistan
2022 C3 of the Year Finalist - Modified
I bet a manual is easier to rebuild than an auto. Rebuilding a T5 at the moment, fairly simple if you got the instructions.
Melting Slicks
Joined: May 2009
Posts: 3,079
Likes: 315
2024 C3 of the Year Finalist - Unmodified
My M21 was leaking and difficult going into second. I pulled it and brought it over to machine shop Bob for tear down, inspection and rebuild. Needed new second gear, new synchros, new thrust bearing and all new seals. Parts were $412 and labor was $428, tax included. Was given lots of photos and the old parts. Would have been way over my head. 
Last edited by Faster Rat; Oct 15, 2011 at 07:43 PM.
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Melting Slicks
Joined: May 2009
Posts: 3,079
Likes: 315
2024 C3 of the Year Finalist - Unmodified
Denpo
I laugh every time I see your avatar. Reminds me of cruising at 80 on my Harley and looking over at my old biker buddy...his loose neck, cheeks and triceps skin flapping in the wind. Opening one's mouth like that would just let bugs in.
I laugh every time I see your avatar. Reminds me of cruising at 80 on my Harley and looking over at my old biker buddy...his loose neck, cheeks and triceps skin flapping in the wind. Opening one's mouth like that would just let bugs in.
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
I rebuilt my fleabay M20 a few years ago; bought the parts from an eBay vendor "kajunjon.com". Quality stuff, worked as advertised. Mine wouldn't go into first when stopped without brute force so I bought a new 1-2 slider along with the regular rebuild kit (bearings, rollers, sychros, seals, etc.). Really, it's a piece of cake. As mentioned before, you may need a press, but everything else is just regular handtools. I downloaded a GM assembly manual from some crooked website ($5 I think) and just followed that. It works beautifully now; shifts like butter. The only thing that is expensive to replace are the gears themselves, it sounds like the synchro teeth on your 3rd gear may be toast causing the hard shifting but (as I did) you may well be able to band-aid it with a new slider for $20-$30. Honestly, if you can read (and clearly you can spell!) you can do this-it's easier than pulling the trans.
Drifting
Joined: Aug 2010
Posts: 1,626
Likes: 140
From: Kanuckistan
2022 C3 of the Year Finalist - Modified
My M21 was leaking and difficult going into second. I pulled it and brought it over to machine shop Bob for tear down, inspection and rebuild. Needed new second gear, new synchros, new thrust bearing and all new seals. Parts were $412 and labor was $428, tax included. Was given lots of photos and the old parts. Would have been way over my head.
There is some details, like the orientation of a certain washer or where to put sealant/grease/whatever you just can't miss with it.
English is not my first language, image work much better than text for me.
Thread Starter
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
My M21 was leaking and difficult going into second. I pulled it and brought it over to machine shop Bob for tear down, inspection and rebuild. Needed new second gear, new synchros, new thrust bearing and all new seals. Parts were $412 and labor was $428, tax included. Was given lots of photos and the old parts. Would have been way over my head.
Thread Starter
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
I rebuilt my fleabay M20 a few years ago; bought the parts from an eBay vendor "kajunjon.com". Quality stuff, worked as advertised. Mine wouldn't go into first when stopped without brute force so I bought a new 1-2 slider along with the regular rebuild kit (bearings, rollers, sychros, seals, etc.). Really, it's a piece of cake. As mentioned before, you may need a press, but everything else is just regular handtools. I downloaded a GM assembly manual from some crooked website ($5 I think) and just followed that. It works beautifully now; shifts like butter. The only thing that is expensive to replace are the gears themselves, it sounds like the synchro teeth on your 3rd gear may be toast causing the hard shifting but (as I did) you may well be able to band-aid it with a new slider for $20-$30. Honestly, if you can read (and clearly you can spell!) you can do this-it's easier than pulling the trans.
Drifting
Joined: Aug 2010
Posts: 1,626
Likes: 140
From: Kanuckistan
2022 C3 of the Year Finalist - Modified
Rebuilt could mean a lot of thing.
Just changed the bearings and seals? also changed the synchro? Changed the gears with worn out synchro teeth?
Lot of things wear out in a transmission, and decision to change this or that part can be subjective.
If I'd buy a rebuilt one I'd take tailhousing and the cover off to check by myself.
With the money I virtually saved I decided to get a G-Force strengthened case, since case warping is the main weakness of those transmission.
I admit, I love to rebuilt things in general, so I may be partial.
Thread Starter
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
Sure, but do you know what you're getting for that.
Rebuilt could mean a lot of thing.
Just changed the bearings and seals? also changed the synchro? Changed the gears with worn out synchro teeth?
Lot of things wear out in a transmission, and decision to change this or that part can be subjective.
If I'd buy a rebuilt one I'd take tailhousing and the cover off to check by myself.
With the money I virtually saved I decided to get a G-Force strengthened case, since case warping is the main weakness of those transmission.
I admit, I love to rebuilt things in general, so I may be partial.
Rebuilt could mean a lot of thing.
Just changed the bearings and seals? also changed the synchro? Changed the gears with worn out synchro teeth?
Lot of things wear out in a transmission, and decision to change this or that part can be subjective.
If I'd buy a rebuilt one I'd take tailhousing and the cover off to check by myself.
With the money I virtually saved I decided to get a G-Force strengthened case, since case warping is the main weakness of those transmission.
I admit, I love to rebuilt things in general, so I may be partial.
