Convert M21 into an M20?
Team Owner
Joined: Jul 1999
Posts: 26,545
Likes: 46
From: Huntersville NC
Re: Convert M21 into an M20? (Flareside)
There's a new one! (at least for me!) You would just swap out a few gears, right? Having no real clue, I will be interested to see the responses you get. The obvious alternative will be to swap your trans with someone who wants the M21 but has an M20. What is your rear end ratio? MJ
Thread Starter
Safety Car
Joined: Dec 1999
Posts: 4,148
Likes: 5
From: Roxbury NJ
Re: Convert M21 into an M20? (MNJack)
Mark, I have the 3:55 rear. The M21 gears, if you ask me, are a little too close together for normal street driving. Hopefully, I can just change a few gears like you suggested. Somehow, I doubt it's that simple...
I don't want to swap the trans, since it's the original numbers matching trans for the car. I have thought about buying a used M20, then putting all the parts into my trans housing. We'll see.
-Joe
I don't want to swap the trans, since it's the original numbers matching trans for the car. I have thought about buying a used M20, then putting all the parts into my trans housing. We'll see.
-Joe
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Re: Convert M21 into an M20? (Flareside)
Joe this is going to be costly. I replaced just 3rd gear and it cost me about 150 for a used gear. To replace all 4 gears and the countershaft would be quite expensive. I have a M20 in mine with the 4.11. I like the low 1st gear and when I had the 3.55 rear it worked very well to.
Melting Slicks
Joined: May 2001
Posts: 2,215
Likes: 170
From: PA
Pro
Joined: Jun 2001
Posts: 683
Likes: 0
From: Calgary
Re: Convert M21 into an M20? (Flareside)
I think all you have to do is change the cluster gear. If I remember correctly, m-20's and m-21's share the same main shaft gears, however I could be wrong. Go to http://www.5speeds.com. They sell individual gears or complete sets for all muncies at quite reasonable prices. The owner (Paul) is a transmission guru and can answer questions personally via the phone number available on his web site. I've dealt with him and recommend him highly!
[Modified by 74vetteman, 12:19 AM 10/16/2001]
[Modified by 74vetteman, 12:19 AM 10/16/2001]
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Thread Starter
Safety Car
Joined: Dec 1999
Posts: 4,148
Likes: 5
From: Roxbury NJ
Re: Convert M21 into an M20? (Gordonm)
Gordon, it looks like I don't have to replace everything. Only the input shaft and the cluster, which run around $350. Sounds like a good winter project.
Thanks everyone!
-Joe
Thanks everyone!
-Joe
Intermediate
Joined: Nov 1999
Posts: 47
Likes: 0
Re: Convert M21 into an M20? (Flareside)
My tranny guy did the swap for free when he rebuilt it. It seems that the close-ratio gears are in more demand. I guess he'll charge the next guy who wants to go to close-ratio. Call around.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Re: Convert M21 into an M20? (paul_64conv)
Yea I did not have my facts straight. Sounds like a good project. It probably needs a rebuild anyway. why not make it like you want. It is not to hard to do if you have the manual or a video.
