[Formulajones]

Lust4Speed is correct, the M-20's are generally quicker and don't need as much rear gear to do it.

The RPM drop in 4th isn't even that detrimental as you already have momentum working for you. Simple physics. It's the getting moving part that is a bigger player.

Many guys in the 60's figured this out when ordering their muscle cars and opted for the M-20 with 3.73's and even 4.10's. Many Z cars were built this way, You'll also find in PS racing that the M-20 is more commonly used as it's a bit quicker. Guys that wanted the M-21 and knew this would order their car with 4.56's and even 4.88's if they knew they were going racing.

My M-20 car with 3.55's will absolutely blow my M-21 car with 3.73's in the weeds and they both make about the same power. The M-20 with 3.55's simply has better gear multiplication up through the gears.

[Formulajones]

Here's an example laid out like Lust4speed explains of my own cars.

The M-20 with 3.55's

8.94 1st gear
6.67 2nd gear
5.18 3rd gear
3.55 4th gear

The M-21 with 3.73's

8.20 1st gear
6.11 2nd gear
4.77 3rd gear
3.73 4th gear

It's clear the M-20 is going to be quicker. At 6000 rpm in 3rd gear with the M-20 I'm going over 90 mph. By then the race is over, the M-21 isn't going to catch me. The best part is the M-20 car cruises a little better. It cruises about 5 mph faster than my 3.73 car at the same rpm. In fact we have daily driven the M-20/3.55 combo for several years and find it a good all around performer that is much more friendly than the M-21/3.73 setup both in traffic and on the highway, and like I said, it's quicker to boot.

[Formulas]

Yeah with a 3.73 gear I bet most stock GM cars with close ratio were 3.90 or better.

It's really a moot point today anyways with 6 speeds available

Also back in the day what were they thinking ?
Not to long before the muncie 4speed. 3 speeds were the standard

I expect 4speeds were in somewhat a response to being able to travel on new roads east to west north to south at higher speeds

I would still put my money on a close ratio 4.11 vrs a wide ratio 3.55 in the 1/4 in a warmed over 66-70 muscle car

[Formulajones]

Actually GM offered many cars with the M-21 and 3.55's. Just from my own personal experience, they are horrible to drive, you won't win very many stop light jaunts with that combo. My son's air cooled bug is quicker than that from a light LOL

A close ratio with 4.11's is essentially an M-20 with 3.55's. Very close to the same thing with the biggest difference now being 4th gear.

M-21's really don't start to shine until you put some 4.56's out back

[Formulas]

I once ran a wide ratio with a 2.73 it was a dog out of the hole,

every part has its niche I never said close ratio is the swizzle in all circumstances and iam not selling anything, someone asked what were they thinking ? Close has its place

[Formulajones]

I don't disagree, I just like M-21's with some rear gear, to the point they aren't really all that friendly on the highway LOL

[i82much]

I have an M23 with the super-wide geometric ratios, almost 3:1 first and equal RPM drops between shifts. 3.54 gears, 28 inch tires, and a 505 with a mild cam and RPM intake. I like it quite a bit for country driving. It’s not an interstate machine but I knew that would be the case going in.

Not bad for a ride on the back roads of eastern WA and north Idaho, though!

[Formulajones]

Originally Posted by i82much

I have an M23 with the super-wide geometric ratios, almost 3:1 first and equal RPM drops between shifts. 3.54 gears, 28 inch tires, and a 505 with a mild cam and RPM intake. I like it quite a bit for country driving. It’s not an interstate machine but I knew that would be the case going in.

Not bad for a ride on the back roads of eastern WA and north Idaho, though!

Have you had it long? Just wondering if you bought it when they were cheaper.

I really do like those but the prices I see on them now, the cheapest I can find is $2800. Yikes, that's the same price as a TKX 5 speed now. I thought those things were around $2000 before.

[i82much]

Originally Posted by Formulajones

Have you had it long? Just wondering if you bought it when they were cheaper.

I really do like those but the prices I see on them now, the cheapest I can find is $2800. Yikes, that's the same price as a TKX 5 speed now. I thought those things were around $2000 before.

Maybe five years? I don’t remember what I paid for it honestly. I just grew up driving a Muncie and didn’t want that to change. I wanted my car to *feel* like it did when I was younger, only be faster and nicer. Hard to explain but it’s what I wanted, and I got it.

I mean I know EFI and a TKO would totally transform it, but then it would just kind of seem like a newer car to me? I kinda like the feeling of cruising at 3000 RPM and cranking the Dokken with the windows down, ya know?

The guy in my avatar is Todd from Beavis and Butthead. If that doesn’t explain it, nothing will.

[Formulajones]

Originally Posted by i82much

Maybe five years? I don’t remember what I paid for it honestly. I just grew up driving a Muncie and didn’t want that to change. I wanted my car to *feel* like it did when I was younger, only be faster and nicer. Hard to explain but it’s what I wanted, and I got it.

I mean I know EFI and a TKO would totally transform it, but then it would just kind of seem like a newer car to me? I kinda like the feeling of cruising at 3000 RPM and cranking the Dokken with the windows down, ya know?

The guy in my avatar is Todd from Beavis and Butthead. If that doesn’t explain it, nothing will.

I know exactly what you mean, I'm very old school. Those that know me personally would probably tell you I'm overboard old school. LOL Basically technology peaked for me about 1979 Our daily drivers are still points and carbs if that tells you anything.

[geeteeohguy]

Originally Posted by Formulas

"M20, 3.23 for all around best driving. 2.20 first? what the he!! was GM thinking?"

Back in the day drag racing was king 2.20 first gear also provided less of a gear spread RPM drop between gears and the 2.20 first ratio also required a taller rear gear which was desireable for 4th gear acelleration

It was a different time thats why 2.20 first was mainly in your flagship GM go fast cars

Gas mileage and weaker low torque 4 cylinders brought in the 5 + speeds just to make those cars work then the 5 + speeds were used in more powerful cars, evolution.

M20's don't have a 2.20 first gear. They have 2.56 or 2.52, depending on the year of the trans. The '63-'65 boxes have the 2.56 first. The M21 has the tall 2.20 first gear.

[John Milner]

I ran a 2.64 low super T10 in one of my cars with a 4:10 gear and ended up swapping in an M22 with a 2.20 low. I think the car slowed down quite a bit after the M22 swap. I'm thinking about taking the M22 back out and re-installing the Super T10. I'm not a fan of the 2.20 low first gear.

[geeteeohguy]

Originally Posted by John Milner

I ran a 2.64 low super T10 in one of my cars with a 4:10 gear and ended up swapping in an M22 with a 2.20 low. I think the car slowed down quite a bit after the M22 swap. I'm thinking about taking the M22 back out and re-installing the Super T10. I'm not a fan of the 2.20 low first gear.

I have an ST10 in my '61 Corvette with a 3.42 first gear and a 2.20 second gear. Great for parades, (which I would never do, ever) but useless on the street with my 383 engine. A 2.64 low would be perfect. I start out in second sometimes, and usually shift from first to third. I keep out of it in low because it's a smoke show and the 3.42 ST-10's have a weak low gear. The only reason I overhauled it was because it had the 904 iron case.
If I bought a new Richmond T-10, it would be the 2.64 unit.

[scott70]

My 70 455 gto has its original M21 and 3.31 rear. Too tall taking off and too short in 4th. The TKX would be great,,,,maybe someday .

[74Grandville]

I put a 2.64:1 and 3.42 rear in my TA. it seems like a great combo with my basic W72 type build.