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06-05-2017, 03:10 PM
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#1 |
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Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,334
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M20 vs M21
The M20 is the "wide ratio" and the M21 is the "close ratio" - but which is better for street driving? I'm not interested in drag racing this one, so just curious as to which set of ratios would make for a better cruiser.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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06-05-2017, 04:32 PM
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#2 |
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Registered User
Join Date: Oct 2009
Location: San Diego, CA
Posts: 39
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Re: M20 vs M21
The M20 would be the better choice. It has a lower 1st gear, the same close ratio spread 1-2-3 (fun), and just a wide gap from 3-4.
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69 GMC shortbed Carbed LM4 - Manual VB TH350 - Gear Vendors OD |
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06-05-2017, 04:34 PM
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#3 |
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Registered User
Join Date: Feb 2011
Location: Modesto, CA
Posts: 2,189
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Re: M20 vs M21
It depends where your engine makes most of its power at what RPM. Regardless of street or racing purposes, you'd still want to shift inside your engines optimal power band.
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06-05-2017, 04:38 PM
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#4 |
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Senior Member
 
Join Date: Dec 2013
Location: Gods country East,Tn
Posts: 8,545
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Re: M20 vs M21
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06-05-2017, 05:08 PM
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#5 |
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Registered User
Join Date: Sep 2001
Location: Fort Wayne, Indiana, USA
Posts: 1,890
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Re: M20 vs M21
The wide ratio was typically used on muscle cars with rear gears around 3.55. The close ratio (M21 and M22) were typically used on muscle cars with 3.73 and numerically higher gears. The M22 was also used in heavy-duty/big CID muscle cars due to the tougher gear-set.
Good Luck! |
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06-05-2017, 08:34 PM
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#6 |
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Registered User
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 7,738
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Re: M20 vs M21
You are talking car 4 speeds? The SM465 is M20 in the trucks as the wide ratio 4 speed.
If we are talking car Muncie 4 speeds you will be MUCH happier with the 2.52/2.56 first gear of the wide ratio trans over the 2.20 first of the close ratio trans.
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44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax |
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06-06-2017, 06:28 AM
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#7 |
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Special Order
  
Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,851
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Re: M20 vs M21
The M20 was designed to be better for regular driving. They were all built for performance, but as the number goes up so does the level of performance.
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