M21- rebuild questions
Thread Starter
Drifting
Joined: Jun 2006
Posts: 1,912
Likes: 12
From: Schaumburg (Chicago) Illinois
M21- rebuild questions
I am doing a frame off rebuild,,,for some insane reason. 
Anyway, I figure nows the time to see what needs to be done to the transmission. Trouble is I don't know! Here are my questions:
How do I know if it needs to be rebuilt? (Other than being kinda noisy, which I believe is normal, especially when driving without carpeting.)
Rebuild kits are only $225 or so. If I can do it myself then I will do it regardless cause it doesn't cost to much.
Can a guy rebuild it himself without special tools?
How complicated it is relative to rebuilding an engine?
What are the best reference materials available to guide me through it? There is a video available from Ecklers.
Who sells good rebuild kits?
Anyway, I figure nows the time to see what needs to be done to the transmission. Trouble is I don't know! Here are my questions:How do I know if it needs to be rebuilt? (Other than being kinda noisy, which I believe is normal, especially when driving without carpeting.)
Rebuild kits are only $225 or so. If I can do it myself then I will do it regardless cause it doesn't cost to much.
Can a guy rebuild it himself without special tools?
How complicated it is relative to rebuilding an engine?
What are the best reference materials available to guide me through it? There is a video available from Ecklers.
Who sells good rebuild kits?
Le Mans Master
Joined: Mar 2001
Posts: 6,240
Likes: 1,013
From: Watkinsville, GA and Glen Cove, NY
Go to http://www.5speeds.com/index.html and buy the video,along with the rebuild kit. Paul is also on the forum here periodically under the name 5speeds. Very knowledgeable and a real good guy.
Bill
Bill
Last edited by 69ttop502; Dec 6, 2007 at 01:24 PM.
Pro
Joined: Aug 2000
Posts: 713
Likes: 1
From: plymouth mass
Here are my two cents worth on Muncie rebuilding. I rebuilt mine a few years ago. You should be able to do it with average mechanical skills. Firstly, you need access to a good press. Secondly I used the 1973 GM overhaul manual. I am sure there are other reference books out there. You should have some sort of manual to refer to during the rebuilding process. Lastly, beware of rebuild kits that have off-shore bearings in them. You want the best bearings available or you will be redoing the transmission prematurely. Try to find a vendor that will answer your questions regarding the kit make up.
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
I'm a weekend car hobbyist, and I put an M20 in my '70 about two years ago from fleabay. Needless to say, it needed rebuilding- it had become nearly impossible to shift into first from a stop. I had successfully rebuilt a couple Ford toploaders before, so I downloaded a GM rebuild manual, bought a kit from 'KajunJon' along with a new 1-2 slider and two days later it was working beautifully. All I needed other than normal hand tools were a pair of large snapring pliers. I got away without the press by bubba-ing the speedo gear off with the end of a large wrench, though you may not get as lucky. If you read the manual TO THE LETTER two or three times before beginning it'll be a piece of cake. Not to offend anybody out there who ever worked for GM but remember these things weren't put together by geniuses in the first place.
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
I am doing a frame off rebuild,,,for some insane reason. Anyway, I figure nows the time to see what needs to be done to the transmission. Trouble is I don't know! Here are my questions:
How do I know if it needs to be rebuilt? (Other than being kinda noisy, which I believe is normal, especially when driving without carpeting.)
Rebuild kits are only $225 or so. If I can do it myself then I will do it regardless cause it doesn't cost to much.
Can a guy rebuild it himself without special tools?
How complicated it is relative to rebuilding an engine?
What are the best reference materials available to guide me through it? There is a video available from Ecklers.
Who sells good rebuild kits?
Anyway, I figure nows the time to see what needs to be done to the transmission. Trouble is I don't know! Here are my questions:How do I know if it needs to be rebuilt? (Other than being kinda noisy, which I believe is normal, especially when driving without carpeting.)
Rebuild kits are only $225 or so. If I can do it myself then I will do it regardless cause it doesn't cost to much.
Can a guy rebuild it himself without special tools?
How complicated it is relative to rebuilding an engine?
What are the best reference materials available to guide me through it? There is a video available from Ecklers.
Who sells good rebuild kits?
Thread Starter
Drifting
Joined: Jun 2006
Posts: 1,912
Likes: 12
From: Schaumburg (Chicago) Illinois
I was told by a guy at work "If it ain't broke don't fix it" And that these things can be tricky. I'm not sold on the tricky part but the trans shifts just fine. It just seems noisy. But I haven't heard an old car, since ,, they weren't old.
I wonder if I just clean it up and change the fluid in it. See what happens. How hard and how hard is it to remove when the body is on the car? Looks like about 4 bolts from the bell housing and 2 on the frame mount, drive shaft, then it should drop right back and down.
Is this about right?
I wonder if I just clean it up and change the fluid in it. See what happens. How hard and how hard is it to remove when the body is on the car? Looks like about 4 bolts from the bell housing and 2 on the frame mount, drive shaft, then it should drop right back and down.
Is this about right?
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
The rebuild kit that I bought was about $200 and included all the seals, gaskets, new countershaft, rollers, input and output shaft bearings, tailshaft bushing, synchros, dogs and retainers. There were several vendors on ebay at the time I bought mine and I'm sure that hasn't changed. I'm certain prices have gone up some by now but still a good deal, and when I see the money some people are advertising 'rebuilt' Muncie transmissions for I can only conclude that the investment was well worth a day of my time.
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
I was told by a guy at work "If it ain't broke don't fix it" And that these things can be tricky. I'm not sold on the tricky part but the trans shifts just fine. It just seems noisy. But I haven't heard an old car, since ,, they weren't old.
I wonder if I just clean it up and change the fluid in it. See what happens. How hard and how hard is it to remove when the body is on the car? Looks like about 4 bolts from the bell housing and 2 on the frame mount, drive shaft, then it should drop right back and down.
Is this about right?
I wonder if I just clean it up and change the fluid in it. See what happens. How hard and how hard is it to remove when the body is on the car? Looks like about 4 bolts from the bell housing and 2 on the frame mount, drive shaft, then it should drop right back and down.
Is this about right?
Its always easy to pull the trans anytime not any big job,
your going to have your hands full with a body off, even an M/21
with no carpet sound barrier and just some fiberglass surrounding
it would sound a little whinney, I would say if its shifting well in
all gears and you did not notice more of a whine in one gear over
another one, trans may already be in pretty good shape. You
can just pull the side cover off take a look at the brass syncros
and gears get a better idea.
Last edited by Little Mouse; Dec 6, 2007 at 10:57 PM.
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Team Owner
Joined: Nov 1999
Posts: 26,679
Likes: 17
From: This vette goes to 11 Milford MA
St. Jude Donor '03-'05
I rebuilt my Super T-10 in my garage. You definitely need good snap ring pliers, and I don't mean the ones with the screw in tips. You also need access to a press for the mainshaft and a broom handle to install the shaft bearings.
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
I rebuilt mine and it was quite easy. I had Paul look at it first since I live near his shop and he told me what he thought it needed. I then replaced those parts with the help of him via email and use of his video. There is one special tool required. The reason I rebuilt it was because of noise which I thought new bearings would fix. Paul told me they were noisy, especially since these trannys are quite old and that the new bearings probably would not help. Bottom line is that the tranny sounded the same after installing the new bearings. If your tranny is in good operating order, I would not suggest rebuilding it in an attempt to get rid of the noise. Good luck! 
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
Mine has a pretty noticeable gear whine when coasting in second gear, but I've actually seen a couple posts on this site where people wanted to install a Muncie just because of their signature noise. If mine hadn't had the shifting problems I probably wouldn't have bothered rebuilding it either. Rebuilding it (specifically installing a new 1-2 slider) DID fix that.
Thread Starter
Drifting
Joined: Jun 2006
Posts: 1,912
Likes: 12
From: Schaumburg (Chicago) Illinois
Mine has a pretty noticeable gear whine when coasting in second gear, but I've actually seen a couple posts on this site where people wanted to install a Muncie just because of their signature noise. If mine hadn't had the shifting problems I probably wouldn't have bothered rebuilding it either. Rebuilding it (specifically installing a new 1-2 slider) DID fix that.
