Identifying Muncie 4 Speeds III by Paul Cangialosi |
The most popular
question has to be that everyone thinks they have the famous "rockcrusher" M22
4 speed. This had the same gear ratios as the M21 but with a heavy duty gearset.
The reason you may ask? Well it wasn't designed so that you could go drag racing
on Saturday night or impress girls in front of Burger King by doing massive hole
shots. It was primarily designed as a road race transmission. The straighter angle
of the gearset produced less heat and less end loading of the gear train. Combined
with high impact alloy gears this 4 speed really pushed the limits of it's aluminum
case in drag race applications. Although the gears are not spur gears ( completely
straight ) they still produced a fair amount of gear noise thus the "Rockcrusher"
name. These 4 speeds sound like a blower drive. For the real gear head the best
documented movie that sports a real M22 in a car is the famous movie " Two Lane
Black Top ". You can really hear this gear box howl in the background as James
Taylor and Dennis Wilson talk at a little over 3 minutes in this youtube clip. Later on we get to see the same
car with new paint in the classic film "American Graffiti" with Harrison Ford
at the helm. Since they used a dummy car for inside dialog shots you miss the
flavor of the M22 in that flick.
The
dead 2.20 first gear ratio which is the same in the M21 is not that good for
off the line acceleration. You would need at least a 4.56 rear end gear to compensate
for the dead first gear. That was OK when gas was cheap in 1967 and you did
not mind pulling 3000 RPM at 50 MPH while going to work. Times and requirements
have changed making both the M21 and M22 the closest ratio production 4 speeds
ever produced but also not practical for today's driving habits unless road
racing is your thing. The new Muncies being built today have some better ratios.Today's examples of the new car gear set ups are Mustang
GT's with a 3.35 1st gear and 3.08 rear. New Camaros with a 2.68 1st gear, 3.73
rear gear and .59 overdrive. ZR1's with a 2.68 1st gear, 3.54 rear gear and
a .59 overdrive. Get the picture? If you want to learn about this stuff DOWNLOAD
our RPM Calculator software for windows its free.
Top countergear is an M22. Lower gear is an M20. Notice the different helix angles of the gears.
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Below left
is an M22 1st gear. Right is an M20 / M21 1st gear.
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