What is the difference between wide ratio and close ratio four speeds.
02-08-2002, 04:29 PM
#1
Racer
Thread Starter
What is the difference between wide ratio and close ratio four speeds.
I have the M20 transmission in my car but was curious of the difference, and what does "close and wide" mean in respect to the gear.
Thank you
Thank you
02-08-2002, 04:45 PM
#2
Re: What is the difference between wide ratio and close ratio four speeds. (Milest)
I don't know what year you have but most M20's were referring to a Muncie.
A Muncie M20 (wide ratio) gear set was 2.52 / 1.88 / 1.46 / 1.00
A Muncie M21 (close ratio) gear set was 2.20 / 1.64 / 1.28 / 1.00
The thinking was that a close ratio trans would have less RPM drop when shifting between gears keeping the engine closer to it's peak HP range.
A Muncie M20 (wide ratio) gear set was 2.52 / 1.88 / 1.46 / 1.00
A Muncie M21 (close ratio) gear set was 2.20 / 1.64 / 1.28 / 1.00
The thinking was that a close ratio trans would have less RPM drop when shifting between gears keeping the engine closer to it's peak HP range.
02-08-2002, 04:48 PM
#3
Race Director
Re: What is the difference between wide ratio and close ratio four speeds. (Pete79L82)
Yes, the RPM drop on a close ratio is alot less. My '68, having the close ratio trans drops about 400rpm's between shifts. My '80, with the wide ratio trans, drops about 650-700rpm's between shifts.
02-08-2002, 04:49 PM
#4
Melting Slicks
Re: What is the difference between wide ratio and close ratio four speeds. (Milest)
in 1975, they were Borg Warner transmissions.
M20 (1)2.64 (2)1.75 (3)1.33 (4)1.00 (R)2.55
M21 (1)2.43 (2)1.61 (3)1.23 (4)1.00 (R)2.35
M20 (1)2.64 (2)1.75 (3)1.33 (4)1.00 (R)2.55
M21 (1)2.43 (2)1.61 (3)1.23 (4)1.00 (R)2.35
02-08-2002, 06:04 PM
#5
Drifting
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Re: What is the difference between wide ratio and close ratio four speeds. (Milest)
The reason for the 2 types of transnissions was to compensate for the rear axle ratio. The m20 was used on 3.36 and numericly lower rears and the m21 was used on 3.70 and numericly higher rears. This was necessay to give you a good mechanical advantage in the lower gears. The lower ratio 1ST and 2nd gear makes it difficult to get to 1 to1 in 4th gear with out a large gap between the other gears. Thats why the rpms fall off more between gears.
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02-08-2002, 10:09 PM
#6
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Re: What is the difference between wide ratio and close ratio four speeds. (ED DINAPOLI)
The reason for the 2 types of transnissions was to compensate for the rear axle ratio. The m20 was used on 3.36 and numericly lower rears and the m21 was used on 3.70 and numericly higher rears.
:cheers:
Pat Kunz
02-09-2002, 08:41 AM
#7
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Re: What is the difference between wide ratio and close ratio four speeds. (73 LS-4)
Pat,
You are correct with the 3.55 rear in 73. Its seams that Chev. was not sure what trans to use on the 3.55 rear. If you look back into the specifications guide you will see it offered as std equipment with the 3.55 in some years and not others. It also mattered what engine option you had. You will also see that in some years you could get the 3.36 rear with the m21 as a special order as well. Chev. made it easy to make your own combination. I did not mean to mislead anyone on this, but for this topic I think it explained the concept of how the rear and the trans was working pair and not just any trans with any rear. You could get a wide box with a 3.70 rear and have a lower 1st gear ratio than a close box with a 4.11rear. Thanks for the heads up.
Ed
You are correct with the 3.55 rear in 73. Its seams that Chev. was not sure what trans to use on the 3.55 rear. If you look back into the specifications guide you will see it offered as std equipment with the 3.55 in some years and not others. It also mattered what engine option you had. You will also see that in some years you could get the 3.36 rear with the m21 as a special order as well. Chev. made it easy to make your own combination. I did not mean to mislead anyone on this, but for this topic I think it explained the concept of how the rear and the trans was working pair and not just any trans with any rear. You could get a wide box with a 3.70 rear and have a lower 1st gear ratio than a close box with a 4.11rear. Thanks for the heads up.
Ed
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