Gentlemen! (and ladies, too)
I've come to the decision it's time for a horsepower increase in for my 72's smallblock. I don't think I'll get any greedier than 400HP, but that's what everybody says. So many factors to take into account. One very important one is can the factory M-21 handle the new horsepower numbers? Naturally, we'll "crack" it open for inspection and renewal of worn parts (lots of metal shavings in the oil). I'm not doing any racing with it, just a little noise around the neighborhood and some sweet music going thru the gears. Upgrading to an M-22 or similar is a little more than I bargained for. Thanks!

JR

I dont think youll have a problem with the m-21 and a small block

my BB came with one..and so did the 400, and 435 hp models in 69..

"converting" your m-21 to m-22 isnt that big of a deal.

if youre going to rebuild the m-21... just get m-22 gears instead.. (especially if you like the sound of a rockcrusher)

except for the gear angle the trasmissions are identical.. same ratio, same casing, everything.

Thanks for replying so quickly....I didn't know that was do-able. Do you have any idea $$$$? Ballpark figure will do. Didn't even know the M-22 had a particular sound. As you can clearly see, I've got a lot to learn still. Thanks a whole lot.

JR

The M-22 is called the "Rockcrusher" because it sounds like it's crushing rocks in operation.

I have an M-21 in my '69 427/435 and believe me, it's a stout transmission. A Rockcrusher must be unbeliveably tough.

Gunslinger said: The M-22 is called the "Rockcrusher" because it sounds like it's crushing rocks in operation.

NO WAY!!! Gotta have it!! I really don't need it, but you know how it is. Why would a woman need more than 5 pairs of shoes?

JR

Q: What is that whining noise coming from my Muncie M22?

A: This noise is normal and has to do with the angle at which the gears mesh. You'll usually hear it in 1st, 2nd, and 3rd gear (but not 4th) after you've accelerated and you then release the gas pedal, letting the engine brake the car. It has almost the same sound in reverse. The M22 gears have a shallower mesh angle, as shown in this photo that compares Muncie gear angles. The shallow angle causes the "whine" noise, and the sound is the reason for the popular nickname for this transmission, the "Rockcrusher." The lower angle increases the load carrying capacity of the gears at the expense of the increased noise. The reason for absence of the noise in 4th gear is that 4th is a direct output from the input (1:1 ratio), and there are no significant gears involved.

gear photo

http://www.camaros.org/trans.shtml#MuncieGearAngles

muncie faq

http://www.camaros.org/trans.shtml#MuncieRatios

jredding said: Thanks for replying so quickly....I didn't know that was do-able. Do you have any idea $$$$? Ballpark figure will do. Didn't even know the M-22 had a particular sound. As you can clearly see, I've got a lot to learn still. Thanks a whole lot. JR

rebuilding your m-21 into an m-22 shouldnt be any more expensive than a FULL rebuild on an m-21.. (you dont always replace the gears.. but since you have quite a few metal shavings... you should.)

perhaps the gears will cost a little more as there is less demand and therefore less supply.

but i doubt it is much more

as for the sounds I always understood it as not sounding like it is crushing rocks, but having that same high pitched compression braking whine a dump truck (or other large construction equipment) has..

These are all the parts you need to convert your worn out Muncie 4 Speed to a M22 "Rock Crusher". Includes the new M22 Gear Set (Input, 1st, 2nd, 3rd, Cluster and Front Reverse Idler Gears); Syncro Assemblies (Hub, Sleeves, rings and Keys with Springs); complete rebuild kit with roller bearings, seals, gaskets, countershaft, small parts and etc. See Pic above.
Cost: Close Ratio 2.20 $845.00
Wide Ratio 2.56 $895.00
Email us at fourgeartrans@aol.com for more information or to place order.

The other reason it is called a rock crusher is the way you have to shift. No easy whimpy shifter movement. It may not go in gear. SLAM IT. It's happy that way. It shifts better and more positive, and it's actually easier then a mosey shift. They do whine. If you break it, I want your engine.

Like the sound a "Pete Jackson" gear drive (timing chain)would make, maybe? You are the gearhead of gearheads, son (no pun intended).

JR