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Discussion Starter · #1 ·
I've been told that the 4 speed that's coupled with my 540 is an M22 Rock Crusher. Can someone out there confirm it by the stampings or do you have to actually look at the gears?



Thanks, Vince
 

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Don't know the numbers but m22's have a very distinctive whine to them because of how the gears are cut. Can you hear it coming from a block away? I love how those things sound. Might get old in a daily driver though.
 

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Even though numbers might point to it being a M-22 after 30-40 years I think you would need to make sure by opening it up and look at the gears.
 

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Discussion Starter · #5 ·
thanks for the input

I'll have to take the side cover off and take a look at the gear angle to be sure.
 

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I'm not sure what year they started it but I think 68 and later the front input shaft on an M22 has no grooves in it. M20=2 grooves, M21=1 groove and M22= 0 grooves. That might help.
 

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Per Chevy by the Numbers

All 1963-69 Muncies maincases, only the M22, was drilled for a drain plug.

After Oct. 21st, 1969 to 1974 a suffix letter was added to to the Assembly Date Code.
A=2.52:1 Wide Ratio M20
B=2:20:1 Close Ratio M21
C=2:20:1 M22 Close Ratio
 

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if i remember right the M22 also uses the same yoke as a TH400...
 

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Per Chevy by the Numbers

All 1963-69 Muncies maincases, only the M22, was drilled for a drain plug.
Not true. Any could have had the drain plug drilled. You cannot tell by the case if it is an M22.

if i remember right the M22 also uses the same yoke as a TH400...
All 1970 and later Muncies have the 32 spline output and 26 spline input. All 69 and ealier have a 10 spline input and 27 spline output

Pull the cover, thats the way I checked mine before I bought it.
Yup. No rings on the input shaft is a good clue, but early M-20s also had no rings. If it has no rings and a 26 spline input, it could be an M-22 if it doesn't have an aftermarket input shaft. You really have to open the side cover to know for sure. In first gear, if the output turns once for each 2.5 turns on the input, it is definitely an M-20 or possibly an Autogear wide ratio M-22.

The numbers stamped on the case were the same for all Muncies in a given year except for 1965. That was the year the M-22 was introduce and it had the 1 inch count shaft.

Also, if it up a 1 inch counter shaft and no rings is most likely an M-22, but if parts have been change, all bets are off. People will bore the early cases to put 1 inch counter shafts in.
 

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AS our learned gentlemen have said

have to look at the gears....
My trans had the casintg number, the correct date number, everything, turned out to be a M20, M-22 isnt that big of a deal anyhow, just a nother part to brag about
LOL
 

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Exactly correct. The only way to tell is to remove the side case. I to have sent many a Muncie to the scrap heap. I've also built many of them from spare parts I had at the shop. There is no true one ring, two ring, no ring, drain plug or no plug way to tell. I've just seen too many exceptions to the "rules".
 

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I have to laugh about this. Back in the day (when we were driving these cars every day) I couldn't TELL you how many Muncie trans we blew, and mixed and matched parts to build others. It never mattered one iota what the case said, only that we got one back together to drive that night. You used to be able to buy them for 50.00-100.00$ all day long. I personally had about fifteen whole trannys and piles of parts (from blown ones) at any one time. They never lasted very long. We always used the wide ratio ones (running lower gears they were better) and sold off the close ratio ones. In all those years, I never ran across an M22 (and I must of had over 100 of 'em). They seem to be coming out of the woodwork now, but you can also buy replacement parts where years back they were very scarce. Bottom line I'd NEVER trust what a case spec'ed out to be, chances someone like me blew it a few times over and mixed parts because driving was what mattered.....
I'm not a fan of the M21/M22 either. When I rebuilt my M-21, I made it an M-20. There are a total of two internal parts that differentiate an M-20 from an M-21 and a total of 5 internal parts that differentiate an M-22 from and M-20 or M-21. My case has a drain plug too.
 

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Back in the early 2000s I built a 22 out of brand-new parts (in a old original 22 case). Haven't ran it yet but now that they make wide ratio M22 gears and the fact that I bought a Supercase with the steel gurdle makes me think I'm going to sell off the 22 close and build a 22 wide.....
The Autogear wide ratio M22 has pretty good gear spacing. The M20 is really nice if you are trying to get to 85 MPH quickly, but the 3 -4 gap is large.
 

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Muncie Musings

I have an M20 on a 3:08 rear-end. INcidentally it is stamped as a '70 and has 10 spline input, 27 spline output, two rings on the main shaft, and a drainplug. Am in the process of trying to get a new M22Z (ultra-wide ratio) from AutoGear for the best of all worlds as far as a 4-speed goes.
 
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