Muncie M20 vs M21?
Le Mans Master
Joined: May 2000
Posts: 6,493
Likes: 6
From: Bloomington MN
Cruise-In II Veteran
Re: Muncie M20 vs M21? (BB wowbagger)
I just switched from and M21 (Muncie) to an M20 (Super T-10) this year. I have 3.70 gears and I must say I like the M20 a lot better. All of the first 3 gears are lower, which makes it easier to drive around town, but the 4th gear is the same, so highway mileage doesn't change (it sucks with either tranny :D ). The M21 would be ideal for a road racer who wants to keep the revs in a certain range all the time.
AC
AC
Heel & Toe
Joined: May 2005
Posts: 20
Likes: 0
im thinking of getting this m20 out of a 69 elcamino, i was wondering am i going to need to get a different shifter becuase its close to the back of the tailhousing on this one, my 76 is a original auto but i wanna drop a stick in it.. i think i need console, pedal assembly, some and some linkages correct?
it has a th350 in it now.
heres a pic of the one i wanna buy he want 450$ comes with clutch adn bellhousing and all i guess
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it has a th350 in it now.
heres a pic of the one i wanna buy he want 450$ comes with clutch adn bellhousing and all i guess
Uploaded with ImageShack.us
Burning Brakes
Joined: Jun 2010
Posts: 1,165
Likes: 93
From: Bellmore NY
I rebuilt my M21 as an M20 behind my 3.36 geared stock LS4. Its not a radical difference out of the hole, but an improvement.
I find the biggest difference is the spread between 3rd and 4th. A downshift from 4th to 3rd in an M21 is very forgiving, very road racy, minimal change of rpm. 4th to 3rd downshift in an M20 causes a noticeable rise in rpm, and does not have the same feel of "finesse" that an M21 has
I find the biggest difference is the spread between 3rd and 4th. A downshift from 4th to 3rd in an M21 is very forgiving, very road racy, minimal change of rpm. 4th to 3rd downshift in an M20 causes a noticeable rise in rpm, and does not have the same feel of "finesse" that an M21 has
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
If you're going with a new tranny, why not a more modern Keisler or Hurst Tremec O.D. set up. A friend with a 79' L-82 3.73 axle car went Keisler 5 speed .68 O.D. and like a whole nother car on the highway.
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Heel & Toe
Joined: May 2005
Posts: 20
Likes: 0
founda rebuilt m21 muncie for 550$ but it doesnt come with flywheel or linkage .. u think its worth the extra 100 bones?
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Drifting
Joined: Oct 2005
Posts: 1,528
Likes: 148
From: East London/SW Essex UK
My L36 '68 is currently running a stock trans and rear, an M21 and 3.55. I don't like this combo one bit, and the day I rebuild the transmission is the day it becomes an M20! I plan to run a 3.36 axle with the M20. This combo would give both a better launch and lower highway revs than my current combo. The L36 makes plenty of torque, so the M21/3.55 is a major mismatch. I honestly can't think of one senario where I would want to run my current combo on the street. Torquey big block, high strung small block, no way.
The M21's 2.20 first gear is way to low for a good launch. Just look at all the aftermarket transmissions today, their first gears are usually 3.00+.
Have you guys seen the new M22 gears that are available with the M20 gear ratios? M22s usually have the M21 ratios. I want one!
The M21's 2.20 first gear is way to low for a good launch. Just look at all the aftermarket transmissions today, their first gears are usually 3.00+.
Have you guys seen the new M22 gears that are available with the M20 gear ratios? M22s usually have the M21 ratios. I want one!
Instructor
Joined: Sep 2005
Posts: 180
Likes: 1
I can tell you from experience that the difference between the m20 and m21 with a 4.11 big block is worth 2 tenths and 2mph in favor of the m20. With a smaller gear it would be more dramatic. The close has better street manners but bad for drag racing and getting out of the hole. I would never want an m21 with anything less than a 3.73. Anybody want to trade a m20 for an m21, I have areal nice new m21
Heel & Toe
Joined: May 2005
Posts: 20
Likes: 0
I can tell you from experience that the difference between the m20 and m21 with a 4.11 big block is worth 2 tenths and 2mph in favor of the m20. With a smaller gear it would be more dramatic. The close has better street manners but bad for drag racing and getting out of the hole. I would never want an m21 with anything less than a 3.73. Anybody want to trade a m20 for an m21, I have areal nice new m21
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
I can tell you from experience that the difference between the m20 and m21 with a 4.11 big block is worth 2 tenths and 2mph in favor of the m20. With a smaller gear it would be more dramatic. The close has better street manners but bad for drag racing and getting out of the hole. I would never want an m21 with anything less than a 3.73. Anybody want to trade a m20 for an m21, I have areal nice new m21
Racer
Joined: Feb 2010
Posts: 425
Likes: 2
I found the M21 and 3.08 rear end a perfect ratio on my L36 - plenty enough torque for easy pull away - short shift in to 3rd or 4th if I wanted (or even pull away in 2nd) - yet I still had the close ratios if I wanted to 'play'. I now have the same set-up, but with a 500+ hp 489 up front - again a really good combination with reduced low-end torque - Question all this talk about higher numerical first gear ratios - are these really needed except in a small block car with close to zero low end torque - surely you will tend to loose most of the theoretical 'advantage' in wheelspin?
Drifting
Joined: Oct 2005
Posts: 1,528
Likes: 148
From: East London/SW Essex UK
I found the M21 and 3.08 rear end a perfect ratio on my L36 - plenty enough torque for easy pull away - short shift in to 3rd or 4th if I wanted (or even pull away in 2nd) - yet I still had the close ratios if I wanted to 'play'. I now have the same set-up, but with a 500+ hp 489 up front - again a really good combination with reduced low-end torque - Question all this talk about higher numerical first gear ratios - are these really needed except in a small block car with close to zero low end torque - surely you will tend to loose most of the theoretical 'advantage' in wheelspin?
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
M22 is a rock crusher because of the gear noise. to reduce gear noise in a normal car, engineers put in a helical cut gear at 44 deg( I believe). THis provides a quite comfortable ride but at the cost of strength and the additional side loading on the tranny case caused by the gear tryto get pushed into the case. THe M22 has 22deg helical cut gears, increasing strength and reducing loading on the case but they are as noisy as all hell.
To the OP if you want to hear an M22 go to you tube put in Two Lane Black Top. There's some videos of the movie with it whining away.
