2:73 gears with Muncie 4 speed

70Znut

Veteran Member
Lifetime Gold Member
Feb 5, 2016
338
Sarasota,FL
I have the Truetrac in my 70 with the 3:73 gear set, has been Rock Solid for years of flogging with zero problems.
 

G72Zed

Veteran Member
Sep 8, 2015
3,911
Canada
I thought all M21/22 where close ratio and had a 2.20 first gear. There’s a reason why I believe all Z28’s from 1967 to 1969 could NOT be ordered with any automatic and nothing under a 3.73.
1970-1972 Z’s had a standard 3.73 gear, option was 4.10, nothing under 3.73’s, GM new why...dog city.
 

G72Zed

Veteran Member
Sep 8, 2015
3,911
Canada
I had the close ratio M22, then road race Doug Nash/Richmond 5 spd, face plated, now TR6060 T56 6spd combined with 3.73/27”
Tire, love it, second gear is 2.10....would never go back ever!!!
I drove an original 72 Z with M21/3.73, boy, so apparent it needed more O/A first gear ratio.
 

Bentley

Veteran Member
Aug 14, 2020
246
I thought all M21/22 where close ratio and had a 2.20 first gear. There’s a reason why I believe all Z28’s from 1967 to 1969 could NOT be ordered with any automatic and nothing under a 3.73.
If your correct, the 302 had alot to do with this decision too.....
 

Todd Devine

New Member
Aug 6, 2021
25
I just confirmed that it is an 8.2 , not an 8.5. I don’t plan on racing or beating it too much.. pretty much a cruiser..local shops want $1600 to $1900 to add gears and posi to the existing housing.
 

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G72Zed

Veteran Member
Sep 8, 2015
3,911
Canada
If your correct, the 302 had alot to do with this decision too.....
Yeppers, no wonder they worked well with 4.56’s.

I’ve driven many M21/2- 3.73 second gens, not enough O/A first gear ratio.

My TR6060 wide ratio Magnum has a 2.97 first, and 2.10 second gear combined with the 3.73/ 12 bolt and 27” tire...that combo has been the absolute best for me.

Best on the bottom, and grab the .80 5th or .63 6th on the highway and get there quickly.

Made a major world of difference, worth every penny.
 

1980RS

Veteran Member
Jun 17, 2006
6,240
MN
Here's a little story I will tell you about manual transmissions I learned back in the 80's. When we all use to race around town most guys back then had 4 speeds and lots were Muncie's. Now you had 3 choices for low gear ratios, 2.56, 2.52 and 2.20 which is the close ratio. After having a couple of close ratio Muncie's I always though they sucked performance wise, why? because they were sheet out of the hole for most bigger engines. I switched to the 2.56 low gear trans and while it was better I though when I started to figure out that the low gear was the key to performance. In 1983 I made the switch to start using Saginaw 4 speeds because even though they are weaker I still won a ton of races with them as the had a 3.11 low gear and a 2.20 2nd gear. I quickly learned that the Mustang 5.0 guys could win a lot of races as the 5 speeds they used in the fox body cars has a 3.27 low gear, so you could race getting quickly out of the hole and still use a decent gear for cruising on the highway, It was called launch ratio. I did break a lot of Saginaw's along the way, but being I could get them used out of all the Vega's, Monza's and other GM cars at $20 bucks a pop from the scrap yards, it didn't matter. One month I went through 5 of them and just bought some more. The key to making them last was not to power shift them which I did learn after some breakage. Sure you can race a 2.20 low gear 4 speed but the question is why? when there are so many good low gear 5 and 6 speed trans options out there these days with O/D. When you can get someone out of the hole by 2-3 cars it's pretty hard for them to catch you.
 




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