Topic: Is there a way to identify an M22 without removing it?
in Forum: C3 Driveline Components
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Hi, I am new here and in the process of getting my 1971 Stingray out of a 13-year hibernation. I was told long ago that I have an M22 tranny, but given the very small number that were made, I have doubts. Is there a way to tell without taking it out of the car? I need some rear body work done and am extremely hesitant to hand it over to a shop given that I might have that very rare tranny.
On the other hand, I am the 3rd owner and have had it since it was only 14 years old, so maybe I do, maybe I don't. Any help would be greatly appreciated!
Thanks!
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Dawn,
Anthony
Most (probably all) Muncie transmissions from 1969 on were stamped "A" for the M-20, "B" for the M-21, or "C" for the M-22.
From the outside, all of the Muncie cases are the same. Only the M-22 was tapped for a drain @ the factory.
The letter will follow the date stamp production code on the passenger side of the tranny. The VIN derivative is also stamped in this area.
An example of a February '71 M-20 stamping would be "P1B13A"
P= Muncie
1= 1971
B=February
13 = 13th day
A= M-20
Hope this helps,
Anthony
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20219
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
If the car is drivable, determining the trans is an M22 is easy...just listen for the noise! They growl quite loudly in all gears.
You could also remove the side/shifter cover, and look at the gears. M22 gears are almost straight-cut...very little angle to them.
While it's true that the M22s had drain plugs..other transmissions did also, so that, in itself is not the determining factor.
The stamp numbers, and a look at the gears themselves is really the only way to know for sure what it is.
You could also remove the side/shifter cover, and look at the gears. M22 gears are almost straight-cut...very little angle to them.
While it's true that the M22s had drain plugs..other transmissions did also, so that, in itself is not the determining factor.
The stamp numbers, and a look at the gears themselves is really the only way to know for sure what it is.
Joel Adams
C3VR Lifetime Member #56 
My Link 
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Oh, and as for the noise, it's been so long I can't truly remember. What I do remember is missing a gear badly in a street race about 20 years ago. My boyfriend told me it should have shredded the gears, but there was no apparent problem :)
Dawn
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20219
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Look in This area for the trans ID stamp. It may be on the driver side, the pass side, or even the top or bottom, but the most common place is driver side, right where I've marked this one.
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Well gentlemen, it appears I have an M-21, disappointing but not wholly unexpected once I realized how few M-22s there were. Here is the stamp:
P1A22BH
at least it looks like an H at the end. There did appear to be drain plugs though.
Sorry it took so long! Just got the brakes fixed, it is nearly ready to actually drive, woohoo!!
Dawn
in Forum: C3 Driveline Components
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