M21trans
Burning Brakes
Joined: Jun 2010
Posts: 1,165
Likes: 93
From: Bellmore NY
Pretty subjective question, but in general, its a "good" transmission. 2.20 1st gear, so I would recommend having something like 3.73 in the rear. Muncies shift well in general. Is it indestructible? No, but its survived behind plenty of heavy hitters from the muscle car era.
Burning Brakes
Joined: Jun 2010
Posts: 1,165
Likes: 93
From: Bellmore NY
I don't think its a bad deal, but find out what year unit it is. Ideally a 26 spline input and 32 output like a th400. Has it been rebuilt?
Here is a quick read for you to get a little more edjamkated. https://www.hemmings.com/magazine/mu...s/1495624.html
Here is a quick read for you to get a little more edjamkated. https://www.hemmings.com/magazine/mu...s/1495624.html
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Is my vette stock?? HAHA
Joined: Oct 2015
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From: Im not allowed to tell you
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The input shaft is the shaft that sticks out the front and engages the clutch. So you need to now how many teeth are in the shaft to match the clutch to. The out put shaft is what the driveshaft slides onto , but if he is selling the shaft with the trans then they will mate up. There are a few 4speed conversion threads around and it can be done, you just need the parts.
So you will be needing a 3 pedal setup, a tab to weld or bolt to the frame for the clutch Z bar, the assorted linkage, a pivot bolt to screw into the engine for the z bar, a correct bell housing for the clutch and flywheel you buy, trans mission mount. The nice thing is the auto cars have a removable trans crossmember so you could feasibly do the swap with the engine in the car.
Smallblock and big block cars used the same chassis frame, so the transmission is always in the same place, the motors just mounted forward or backward
I have a m21 in front of a 3.55 rear end, it is not ideal. The car will go but getting it to start out of the stop lights can cause a smelly clutch. Im changing it to a M20 gearing. If I ever find a 3.70 rear end I'll swap it back
So you will be needing a 3 pedal setup, a tab to weld or bolt to the frame for the clutch Z bar, the assorted linkage, a pivot bolt to screw into the engine for the z bar, a correct bell housing for the clutch and flywheel you buy, trans mission mount. The nice thing is the auto cars have a removable trans crossmember so you could feasibly do the swap with the engine in the car.
Smallblock and big block cars used the same chassis frame, so the transmission is always in the same place, the motors just mounted forward or backward
I have a m21 in front of a 3.55 rear end, it is not ideal. The car will go but getting it to start out of the stop lights can cause a smelly clutch. Im changing it to a M20 gearing. If I ever find a 3.70 rear end I'll swap it back
Last edited by Rescue Rogers; Nov 19, 2018 at 06:54 AM.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
The 10 spline Muncies are weaker than the later 26 spline gear boxes. The counter shaft is smaller in the early ones and I have seen many of them litter the track under hard launches. If you drive it without slicks and don’t have a ton of HP it will live just fine behind a SB motor. I personally don’t like the M21 for the street. They were designed for road racing and drag racing to keep the rpms in the range to maximize the HP. The wide ratio M20 is a better street gear box. With a 2.20 ratio first gear you need deep gears to get the car moving. $1000 for the setup may not be a bad price but what condition is the trans. If it as a ton of miles or has been thrashed over the years it may need a rebuild which could run a lot of $$$.
Is my vette stock?? HAHA
Joined: Oct 2015
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
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the smaller counter shaft was used through 64 I believe so that shouldnt be an issue for you
Race Director
Joined: Dec 1999
Posts: 19,610
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From: Forked River NJ
Thread Starter
Advanced
Joined: Sep 2018
Posts: 85
Likes: 7
Rescue rogers ,thanks for your help with this the guy selling trans/driveshaft/shifter setup. Plus shipping to r.i. All for 1.000 .00 my car is a 1970 body and a 76 small block and a 1976 frame that had a manual trans.the part on the frame for the z bar is there.so will this all fit or should i just keep my 400.but i do like the idear of a 4speed thanks remember the 76 motor-problem or not
Melting Slicks
Joined: Sep 2004
Posts: 3,226
Likes: 667
From: Northeast
If you live in RI then you know that the prices for Muncie's on Craiglist range from $750-$1200 with the latter being rebuilds. One guy is selling a rebuilt for $1000 with a guarantee. These are just for the transmission but if you can get linkage, etc. for $1000 it is a good price. Looking at ZIP, the linkage is $75, boot $25, shifter $90. Has it been rebuilt? I don't know that I would send someone $1000 without a careful inspection. Ears might have been broken, chewed up gears, etc. There is a guy in Vermont that has nice stuff (met him at New England Dragway swapmeet) but expensive. Helped my brother last month with his 71 Chevelle BB to go from an auto to Muncie and learning all that extra stuff adds up. He is hoping between used and new to come in @$2000. We had to drop the trans and engine a few inches to get to those top 2 bellhousing bolts. Unsure if that is difficult on a vette but we used an 30" extension with swivel rather than piecing together smaller ones. Good luck with the swap.
Is my vette stock?? HAHA
Joined: Oct 2015
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From: Im not allowed to tell you
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Sounds like you will just need the pedal assembly. Having the z bar tab there makes it easier, you'll still need the little ball the bolts into the engine. They're cheap if I remember right if he didnt include it with the z bar.
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,211
Likes: 9,350
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
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You may have to figure out the speedometer cable. I dont know if the auto trans and 4 speed use the same cable for your year(s).
Then what color speedometer gear you have in the 4spd and try and figure out what gear you need for your rear end
Then what color speedometer gear you have in the 4spd and try and figure out what gear you need for your rear end
