Muncie M20 vs M21?
#2
Le Mans Master
Re: Muncie M20 vs M21? (Ki m Le)
One has close ratios the other has wide ratios.
M-20 M-21
1st 2.52 2.20
2nd 1.88 1.64
3rd 1.46 1.28
4th direct direct
I love my M-21. The gear spacing is tight, the revs are always up. Lots 'o fun. Gear selection all depends on the power curve the engine puts out.
[Modified by burners, 2:57 PM 11/5/2002]
M-20 M-21
1st 2.52 2.20
2nd 1.88 1.64
3rd 1.46 1.28
4th direct direct
I love my M-21. The gear spacing is tight, the revs are always up. Lots 'o fun. Gear selection all depends on the power curve the engine puts out.
[Modified by burners, 2:57 PM 11/5/2002]
#6
Re: Muncie M20 vs M21? (Ki m Le)
They were installed in cars with different differential gear ratios. 3:70 and numerically higher were given the M-21, 3:55 and lower were given the M-20. The lower first gear in the M-20 got the highway geared cars off the line better.
#7
Re: Muncie M20 vs M21? (74vetteman)
Also, the higher gear reduction of the M-20 will probably make it slightly weaker due to more torque multiplication. However, mine is living behind almost 500 ft/lbs, and plenty of drag racing. Good thing I am running street radials though!!
#8
Melting Slicks
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Re: Muncie M20 vs M21? (74vetteman)
They were installed in cars with different differential gear ratios. 3:70 and numerically higher were given the M-21, 3:55 and lower were given the M-20. The lower first gear in the M-20 got the highway geared cars off the line better.
:cheers:
Pat Kunz
#9
Re: Muncie M20 vs M21? (73 LS-4)
[QUOTE]They were installed in cars with different differential gear ratios. 3:70 and numerically higher were given the M-21, 3:55 and lower were given the M-20. The lower first gear in the M-20 got the highway geared cars off the line better.
not nescessarily true, there was a standard gear ratio with an M-20 or 21 but there were also optional gear ratios and this depended on year, my 73 was originally a 3.36 with an M-21, now it's a 3.55 and a much better combination in my oppinion with the M-21.
My bad! Well, take what I said as a rule of thumb, not necessarily in every case. :cheers:
not nescessarily true, there was a standard gear ratio with an M-20 or 21 but there were also optional gear ratios and this depended on year, my 73 was originally a 3.36 with an M-21, now it's a 3.55 and a much better combination in my oppinion with the M-21.
My bad! Well, take what I said as a rule of thumb, not necessarily in every case. :cheers:
#10
Melting Slicks
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Re: Muncie M20 vs M21? (74vetteman)
Also, the higher gear reduction of the M-20 will probably make it slightly weaker due to more torque multiplication. However, mine is living behind almost 500 ft/lbs, and plenty of drag racing. Good thing I am running street radials though!!
#11
Burning Brakes
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Re: Muncie M20 vs M21? (Schmucker)
Thank you all for replied. I have the 427, L36 motor, M20 and M21 ) Muncie just over hauled them myself with all the part for conversion to manual from Auto. The car is 69 vert # matching with 350, 300HP, TH400 and 3:36 rear. All of # matching stuffs will be stored away for originality. With your inputs, I have to make a decision which Muncie to put in the car. BTW, It's going to be street driven car and occasionally, racing against the guy at work with a 64 GTO with 389, M20.and 3:55 rear. I don't want to be defeated again!
Thanks
[Modified by Ki m Le, 7:20 AM 11/6/2002]
Thanks
[Modified by Ki m Le, 7:20 AM 11/6/2002]
#12
Safety Car
Re: Muncie M20 vs M21? (Ki m Le)
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!
#14
Melting Slicks
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Re: Muncie M20 vs M21? (OatBoy)
why is it sometimes called the "rock crusher" thats what i wanna know :cheers:
#15
Re: Muncie M20 vs M21? (Flareside)
Switching from a M21 to a M20 wont change you highway cruse RPM's at all. Fourth gear is 1 to 1 in m20, M21 and M22. You can only lower your highway RPM by increasing your tire diameter, lowering your rear gear ratio or putting in a overdrive unit or transmission.
#17
Safety Car
Re: Muncie M20 vs M21? (OatBoy)
why is it sometimes called the "rock crusher" thats what i wanna know :cheers:
#18
Le Mans Master
Re: Muncie M20 vs M21? (OatBoy)
Only the M22 trans is called "The rock crusher". From what I understood, it was because of the sound the gears made while driving. They aren't exactly known for "silent running" ;)
Dep
Dep
#19
Melting Slicks
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Re: Muncie M20 vs M21? (Dep)
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.