2:73 gears with Muncie 4 speed

secondgenaddict

Veteran Member
Dec 29, 2012
452
Upstate South Carolina
The close ratio box is for road racing, where rarely do you ever come to a complete stop, however more than occasionally you do need to corner at varying speeds slower than flat out, it is in these corners where a slightly different ratio would be most beneficial in keeping the engine within the meat of the torque curve upon exit of the turn for accelerating into the next straight.

If two guys bought new 69 Z28's both with 4.10 rears, one with the M22, the other with the M20. They are out doing stop light pulls one night, the guy with the M22 would swear there absolutely has to be something wrong with his car.
 

kenny77

Veteran Member
Lifetime Gold Member
Jul 31, 2001
3,275
Ft. Lauderdale, FL
Someone out there is making new Muncies with a high first gear in them. Called an M 22 Z I think? Anyway it's made to use like a 2:73 or 3:08 rear gear for great stoplight performance AND cruising RPMs

https://www.trifive.com/threads/my-thoughts-on-m22-z-trans-and-3-08-gears.120602/
A little background info on the M-22 "Z"

September 9, 2009 AUTO GEAR COMPANY, INC. of Syracuse, New York is pleased to announce their latest alternative gearset for General Motor's iconic Muncie four-speed.

The 'M22Z' (ratios 2.984/2.043/1.468/1.000) was designed to provide 'cruisers' an alternative to expensive overdrives. According to the company's Chief Engineer, George Sollish, "Now Muncie drivers can have the highway rpms of a fast axle without changing their gearbox. In addition, when paired with a 3.08 axle the M22Z gearset provides the same 1/2 punch of our successful M22W/3.54 combo, so there's no embarassment leaving a light, either. And like all our gearsets, the M22Z can be used in original equipment cases.
 
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Todd Devine

New Member
Aug 6, 2021
26
Just picked my car up from the shop after getting 3.73 gears and posi carrier installed. Drives like a completely different car!! Only thing is the 3500 rpm’s at 70 on the freeway. I will most likely upgrade to a tremec TKX in the future.
 

jeff swisher

Veteran Member
Apr 26, 2018
1,957
Yukon Oklahoma
@Todd Devine the math puts your car at 70 with 25" diameter tire.

I ran short tires around town and when i went on long trips or actually to the fishing /hunting spot 160 miles away I stuck my 31" tall tires on.

With the .81 OD of that TKX a 31 " tire would bet you the same rpm.

Not that everyone has a set of 31" tires that will actually fit in the wheel wells.
 

accelo

Member
Jan 12, 2015
52
washington
I had a z20 302 in a 1971 Camaro with 3:08 gears. It was a dog motor and would do over 60 mph in first gear.
I removed the motor and installed it in a car with 3;73 and I would have sworn it was a different motor it ran so much better.
If it's for fun I would run 3:55 gears. If you run it on the highway and gas is your only concern run the 2:73.
Yes it will be a complete slug. Over-drives are the way to go.
However, consider the miles you may drive this a year (1000 maybe) its not going to pay for an overdrive.
Consider at 1000 miles and 10mph your cost is $500, a year, for fuel
If you got 20mph it's $250. So you save $2500 in ten years.
It will be so much more fun with the 3:55's. Exception being at highway speeds.
Remember they drove at 2500 to 3000 rpm all the time in the 60 and 70's.
It just no longer feels correct because we are used to 1500 to 1800 rpm at 70 now days.
There is a 30% difference between 2.73 and 3.73. Almost exactly the same as if you had 3.73 and an overdrive transmission.
However the gear ration in first gear is the difference. (First gear ration * differential ration for the final ration in first) (8.2 or 6.1) This is the reason it will be a dog.
Your choice, have fun, drive fast, stay alive.
 
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76z28

Veteran Member
Jun 29, 2009
2,588
bakersfield
I had a real z20 302 in a 1971 Camaro with 3:08 gears. It was a dog motor and would do over 60 mph in first gear.
I removed the motor and installed it in a car with 3;73 and I would have sworn it was a different motor it ran so much better.
If it's for fun I would run 3:55 gears. If you run it on the highway and gas is your only concern run the 2:73.
Yes it will be a complete slug. Over-drives are the way to go.
However, consider the miles you may drive this a year (1000 maybe) its not going to pay for an overdrive.
Consider at 1000 miles and 10mph your cost is $500, a year, for fuel
If you got 20mph it's $250. So you save $2500 in ten years.
It will be so much more fun with the 3:55's. Exception being at highway speeds.
Remember they drove at 2500 to 3000 rpm all the time in the 60 and 70's.
It just no longer feels correct because we are used to 1500 to 1800 rpm at 70 now days.
Your choice, have fun, drive fast, stay alive.
It takes forever for an overdrive to pay for itself(well in my case I get about double what I was getting for MPG, but don't drive much)

I can say the sanity it saves is worth every penny. 3500rpm for me is 103mph(gps tested).

75mph is about 2200 which is perfect

It isn't loud or you don't feel like you're "pushing" the car
 

Todd Devine

New Member
Aug 6, 2021
26
Well , After driving on the freeway a couple of times and realize that my driveshaft needs rebuilding and my Muncie speedo gear needs replacement I decided to stop putting money in a setup that I know I would eventually one day be upgrading.

I ordered the Tremec TKX kit from American Powertrain that includes everything I need including custom driveshaft.
I look forward to getting this installed and should have the best of both worlds…. Good off the line with the 2.87 first gear and .68 overdrive.
 




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