Gear ratio difference between M20, M21, M22 ??
09-11-2008, 11:22 PM
#1
Instructor
Thread Starter
Gear ratio difference between M20, M21, M22 ??
I just read a great article on the difference between wide ratio and close ratio trannys, but would like to know from those that have been dirving them a while, rather than just reading an article:
--> Please confirm or correct my understanding below:
M20 - Wide Ratio
1st--------2nd-----3rd-----4th
(Has a lower ratio 1st gear, and 2-3-4 are a little further apart than the M21 and M22)
M21, M22 - 1st, 2nd, 3rd, and 4th are closer together
1st----2nd---3rd---4th
Have higher 1st gear ratio and all 4 gears are closer together
** M22 has same gear ratio as M21
** M22 gears have less angle which reduces friction (heat)
----------------
-----------------
----------------
Any particular pros/cons of the M20 ?
Thanks
Mike
--> Please confirm or correct my understanding below:
M20 - Wide Ratio
1st--------2nd-----3rd-----4th
(Has a lower ratio 1st gear, and 2-3-4 are a little further apart than the M21 and M22)
M21, M22 - 1st, 2nd, 3rd, and 4th are closer together
1st----2nd---3rd---4th
Have higher 1st gear ratio and all 4 gears are closer together
** M22 has same gear ratio as M21
** M22 gears have less angle which reduces friction (heat)
----------------
-----------------
----------------
Any particular pros/cons of the M20 ?
Thanks
Mike
09-11-2008, 11:28 PM
#2
Le Mans Master
Sort of.
The M-20 was a close ratio-- 2.20:1 low gear and less split between the gears until 4th @ 1:1.
The M-21 and M-22 were both a 2.54:1 low.
The M-22, AKA "Rockcrusher" had straight cut gears and was the stronger of the Muncie gearboxes. Made more noise too.
I have heard the M-22 was also available as a 2.20 close ratio box, but given the intended use of those days, I tend to discount that as the close ratio was better suited to road race applications to keep the engine in the torque band.
The M-20 was a close ratio-- 2.20:1 low gear and less split between the gears until 4th @ 1:1.
The M-21 and M-22 were both a 2.54:1 low.
The M-22, AKA "Rockcrusher" had straight cut gears and was the stronger of the Muncie gearboxes. Made more noise too.
I have heard the M-22 was also available as a 2.20 close ratio box, but given the intended use of those days, I tend to discount that as the close ratio was better suited to road race applications to keep the engine in the torque band.
09-11-2008, 11:43 PM
#3
Instructor
Thread Starter
Sort of.
The M-20 was a close ratio-- 2.20:1 low gear and less split between the gears until 4th @ 1:1.
The M-21 and M-22 were both a 2.54:1 low.
The M-22, AKA "Rockcrusher" had straight cut gears and was the stronger of the Muncie gearboxes. Made more noise too.
I have heard the M-22 was also available as a 2.20 close ratio box, but given the intended use of those days, I tend to discount that as the close ratio was better suited to road race applications to keep the engine in the torque band.
The M-20 was a close ratio-- 2.20:1 low gear and less split between the gears until 4th @ 1:1.
The M-21 and M-22 were both a 2.54:1 low.
The M-22, AKA "Rockcrusher" had straight cut gears and was the stronger of the Muncie gearboxes. Made more noise too.
I have heard the M-22 was also available as a 2.20 close ratio box, but given the intended use of those days, I tend to discount that as the close ratio was better suited to road race applications to keep the engine in the torque band.
I thought the M20 was a wide ratio and M21/M22 were close ratio.
http://www.yearone.com/updatedsingle...nfo/muncie.asp
Last edited by ACMESPEED; 09-11-2008 at 11:45 PM.
09-12-2008, 12:45 AM
#4
Drifting
Sort of.
The M-20 was a close ratio-- 2.20:1 low gear and less split between the gears until 4th @ 1:1.
The M-21 and M-22 were both a 2.54:1 low.
The M-22, AKA "Rockcrusher" had straight cut gears and was the stronger of the Muncie gearboxes. Made more noise too.
I have heard the M-22 was also available as a 2.20 close ratio box, but given the intended use of those days, I tend to discount that as the close ratio was better suited to road race applications to keep the engine in the torque band.
The M-20 was a close ratio-- 2.20:1 low gear and less split between the gears until 4th @ 1:1.
The M-21 and M-22 were both a 2.54:1 low.
The M-22, AKA "Rockcrusher" had straight cut gears and was the stronger of the Muncie gearboxes. Made more noise too.
I have heard the M-22 was also available as a 2.20 close ratio box, but given the intended use of those days, I tend to discount that as the close ratio was better suited to road race applications to keep the engine in the torque band.
Cheers,
Pete
09-12-2008, 02:12 AM
#5
Instructor
Member Since: Jan 2005
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I found this little calculating program:
http://www.stl-vettes.com/65Vette/Tr...ns_Gearing.htm
It contains all the gearboxes you can think of and you can calculate your speed in all the gears with different rearends and tire-size.
It's very helpfull when you have to deside what box, gear and tire you should go for
Best regards, DK.
http://www.stl-vettes.com/65Vette/Tr...ns_Gearing.htm
It contains all the gearboxes you can think of and you can calculate your speed in all the gears with different rearends and tire-size.
It's very helpfull when you have to deside what box, gear and tire you should go for
Best regards, DK.
09-12-2008, 03:36 AM
#6
Le Mans Master
IMHO save the close ratio gearsets of the M22 for use ahead of 3.73:1 and larger ratio rear ends, and FWIW I wouldn't go smaller than a 3.36:1 rear gear even with a wide ratio Muncie box. Forget the Muncie OD, unless it's going in your pickup truck.
BTW, you can now buy high-quality M22 "rock crusher" style wide ratio gearsets! Tops on my Christmas wish list...
BTW, you can now buy high-quality M22 "rock crusher" style wide ratio gearsets! Tops on my Christmas wish list...
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EarlyC34me (10-03-2017)
09-12-2008, 06:32 AM
#7
Race Director
I think you have it backwards there Tim. The regular 4-speed M-20 has ratios of 2.52:1, 1.88:1, 1.47:1 and 1:1. The M-21 close ratio and M-22 close ratio heavy duty ratios are: 2.2:1, 1.64:1, 1.27:1, and 1:1. Reference: Corvette Black Book, and 1969 Owners Manual.
Cheers,
Pete
Cheers,
Pete
09-12-2008, 04:45 PM
#10
Team Owner
Member Since: Nov 2004
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Auto Gear choice of gear ratios in their 4 speeds M22 trans is:
2.20/1.64/1.27/1.00
Then, they have a racing M22x with same first as the M22 standard:2.20 but 1.50/1.17 for second and third gears, fourth at 1.00, am i right saying that the X type have closer second and third gears and that they would be most suitable for a winding mountain road then a wide or standard M22? Specially matched to a 4.11 rear diff gears?
I'm a bit confused about all this iussue, I'm planning changing my 4 speeds trans soon now but i want to be sure i get the right one for my application, way of driving and type of roads (hillclimb/sharp bends).
2.20/1.64/1.27/1.00
Then, they have a racing M22x with same first as the M22 standard:2.20 but 1.50/1.17 for second and third gears, fourth at 1.00, am i right saying that the X type have closer second and third gears and that they would be most suitable for a winding mountain road then a wide or standard M22? Specially matched to a 4.11 rear diff gears?
I'm a bit confused about all this iussue, I'm planning changing my 4 speeds trans soon now but i want to be sure i get the right one for my application, way of driving and type of roads (hillclimb/sharp bends).
09-12-2008, 04:59 PM
#11
Team Owner
Mike, you got it right. All of the 4spds have a 4th gear that is 1:1, so the M-20 has a lower ratio 1st gear than the M-21. (A lower gear ratio, but a higher number) For this reason, the M-20 could be teamed up with a lower ratio rear like a 3.08, while the M-21 needed a 4.11 or a 3.70 to get off the line with the higher 1st gear.
I have an M-20 and it is a nice, evenly spaced trans. I have heard people complain that with the M-21 they shift gears and need to shift again right away, so it's not the greatest for street driving.
I have an M-20 and it is a nice, evenly spaced trans. I have heard people complain that with the M-21 they shift gears and need to shift again right away, so it's not the greatest for street driving.
09-19-2008, 11:40 AM
#12
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Then, they have a racing M22x with same first as the M22 standard:2.20 but 1.50/1.17 for second and third gears, fourth at 1.00, am i right saying that the X type have closer second and third gears and that they would be most suitable for a winding mountain road then a wide or standard M22?
I usually have racers sometimes purchase 2 boxes for different tracks.
Want to learn about ratios? Here is a bit that was published in my book: http://www.5speeds.com/ratios.html
Want to see how we do the roadrace Muncies?:http://www.5speeds.com/spec25
09-19-2008, 02:24 PM
#13
Le Mans Master
It sounds like you have a M-21. I have a M-20 and hate it. For normal driving, 2nd gear is useless. I never use it. It seems like they took a 3 speed box and just added another gear between 1st and 2nd. 1st, 2nd and 3rd are just too close together for my liking.
09-19-2008, 04:58 PM
#14
Team Owner
No, I have the M-20 wide ratio. It is easy (FOR ME!!) to get confused...
lemme think.... ouch! that hurts my head.
M-20 is wide ratio.. that's what I have M-20 + 3.36 decent combination for street driving.
M-21 is close ratio, shift from 2nd to 3rd and you can't tell the difference...
right?
some good info here:
http://www.5speeds.com/muncie2.htm
ahhh!!
Found the 2 articles I was looking for.. these are very good!!http://www.corvettemagazine.com/1999...1/munciep1.asp
http://www.corvettemagazine.com/1999...2/munciep1.asp
Last edited by PRNDL; 09-19-2008 at 05:03 PM.
06-20-2015, 07:49 PM
#15
Le Mans Master
There is NO difference between the gears and ratios of the M20 (wide ratio) and M21 (close ratio) transmissions. The GEARS are the same.....
However, the wide ratio intermediate shaft turns at 1.1 times the rate of the close ratio intermediate shaft, so the drop in revs between 1st, 2nd, and 3rd gears is the same in both transmissions............BUT, the drop to 4th gear (1:1 in both transmissions) is (about) 500rpm in the close ratio transmission, and (about) 1500rpm in the wide ratio transmission.
With (say) a 4.11 rear and CR trans, you have about the same torque mulitplication and acceleration in 1st, 2nd, and 3rd, as you do with (say) a 3.36 rear and a wide ratio transmision. BUT when you shift to 4th (with a 3.36) you now have relatively low revs and relatively good gas mileage for road trips and cruising. So....you could (in Mexico) go street drag racing in 1st thru 3rd, WIN your race, and then shift to 4th and drive home at 150mph, or at 80 with (relatively) good fuel mileage.
However, the wide ratio intermediate shaft turns at 1.1 times the rate of the close ratio intermediate shaft, so the drop in revs between 1st, 2nd, and 3rd gears is the same in both transmissions............BUT, the drop to 4th gear (1:1 in both transmissions) is (about) 500rpm in the close ratio transmission, and (about) 1500rpm in the wide ratio transmission.
With (say) a 4.11 rear and CR trans, you have about the same torque mulitplication and acceleration in 1st, 2nd, and 3rd, as you do with (say) a 3.36 rear and a wide ratio transmision. BUT when you shift to 4th (with a 3.36) you now have relatively low revs and relatively good gas mileage for road trips and cruising. So....you could (in Mexico) go street drag racing in 1st thru 3rd, WIN your race, and then shift to 4th and drive home at 150mph, or at 80 with (relatively) good fuel mileage.
Last edited by 63Corvette; 06-20-2015 at 07:55 PM.
06-20-2015, 11:59 PM
#16
Le Mans Master
Year 1966-1974 Type: M20 Ratio: 2.52 / 1.88 / 1.46 / 1.00 / 3.11
Year 1963-1974 Type: M21 Ratio: 2.20 / 1.64 / 1.28 / 1.00 / 2.27
http://www.5speeds.com/muncie2.htm
However, the wide ratio intermediate shaft turns at 1.1 times the rate of the close ratio intermediate shaft,
BTW, this thread is 7 years old.
06-21-2015, 12:03 AM
#17
Race Director
There is NO difference between the gears and ratios of the M20 (wide ratio) and M21 (close ratio) transmissions. The GEARS are the same.....
However, the wide ratio intermediate shaft turns at 1.1 times the rate of the close ratio intermediate shaft, so the drop in revs between 1st, 2nd, and 3rd gears is the same in both transmissions............BUT, the drop to 4th gear (1:1 in both transmissions) is (about) 500rpm in the close ratio transmission, and (about) 1500rpm in the wide ratio transmission.
With (say) a 4.11 rear and CR trans, you have about the same torque mulitplication and acceleration in 1st, 2nd, and 3rd, as you do with (say) a 3.36 rear and a wide ratio transmision. BUT when you shift to 4th (with a 3.36) you now have relatively low revs and relatively good gas mileage for road trips and cruising. So....you could (in Mexico) go street drag racing in 1st thru 3rd, WIN your race, and then shift to 4th and drive home at 150mph, or at 80 with (relatively) good fuel mileage.
However, the wide ratio intermediate shaft turns at 1.1 times the rate of the close ratio intermediate shaft, so the drop in revs between 1st, 2nd, and 3rd gears is the same in both transmissions............BUT, the drop to 4th gear (1:1 in both transmissions) is (about) 500rpm in the close ratio transmission, and (about) 1500rpm in the wide ratio transmission.
With (say) a 4.11 rear and CR trans, you have about the same torque mulitplication and acceleration in 1st, 2nd, and 3rd, as you do with (say) a 3.36 rear and a wide ratio transmision. BUT when you shift to 4th (with a 3.36) you now have relatively low revs and relatively good gas mileage for road trips and cruising. So....you could (in Mexico) go street drag racing in 1st thru 3rd, WIN your race, and then shift to 4th and drive home at 150mph, or at 80 with (relatively) good fuel mileage.
10-03-2017, 03:08 PM
#20
Drifting
No, they are not the same...
Year 1966-1974 Type: M20 Ratio: 2.52 / 1.88 / 1.46 / 1.00 / 3.11
Year 1963-1974 Type: M21 Ratio: 2.20 / 1.64 / 1.28 / 1.00 / 2.27
http://www.5speeds.com/muncie2.htm
Really? How does it do that?
BTW, this thread is 7 years old.
Year 1966-1974 Type: M20 Ratio: 2.52 / 1.88 / 1.46 / 1.00 / 3.11
Year 1963-1974 Type: M21 Ratio: 2.20 / 1.64 / 1.28 / 1.00 / 2.27
http://www.5speeds.com/muncie2.htm
Really? How does it do that?
BTW, this thread is 7 years old.