Hi

I have a 4-spd that I am trying to identify. Any help would be appreciated. The main housing has the following numbers. On the right side 3925660 US PATENT NO 3088330. On the right side of the tail piece is 3857584 GM. Then stamped on the edge between the two pieces is: 18S404327 P8R31. Thanks for any help given.

Craig

My book says it is a M-22 Rock Crusher with 2.20 first gear and if it has Side Cover part # 3950306 it is a 69 and if it says 3884685 it is a 68. Sounds like a good piece of hardware and a rare one.

Craig,
After the P8R31, SOMEWHERE, there should be an A, B or C. It may not be the same type or size of stamp as the others, and it may not have the same spacing. It could be over a little by itself. Anyway, this letter is what specifies which Muncie you have.
A=M20
B=M21
C=M22
The only way to KNOW FOR A FACT if it is an M22, is to pull the side cover and look at the angle of the gear teeth. Also, an M20, wide ratio will have 2 grooves around the input splines and the M21 will have one groove. An M22 will probably have none. But replacement input shafts usually have none either.

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By gosh, you're right again, DZ. This trans was built on October 31, 1968, and the ABC stamps were to be started on Oct 21st. Apparently this one slipped through the cracks?
Here's a second, and even better question...It was installed in a '68 Vette???(S-St. Louis??) when was the Vette model year changed??? How can this trans be dated Oct 31st, 1968 and be installed in a '68 car??? By the VIN this would've been the 4237th car built, but not built until November '68????? Somethings fishy here...maybe trans date mis-stamped...S/B P7R31??? or maybe someone was trying to fool someone with a bad VIN stamp??? Hmmmmm...

[This message has been edited by Dave Birdwell (edited 07-16-99).]

Hi
An update on this trans I have that keeps getting more interesting all the time.
1)Side cover plate is 3884685 which according to plain69 it is a 68. 2)This trans came out of 1960 Vette. 3)I looked all over the area after P8R31 and could not find any A,B,C. I know P=Muncie 8=1968 How does R translate to October? If there are any other codes to look for let me know and I'll look.

I hope my info was a little helpful I got it out of the Muscle Car review Sept 1999 issue.
The others are right also somebody could have obliterated the trans and put all different guts in it. I hope it still has the straight cut gears for you and has the M-22 guts.

This one is a little confusing to me and I am NOT going to make any authorative statements.
But here is what I see. The VIN looks like a 68 Vette VIN, except the first number should be a 7 and not a 1, I think. A 660 maincase is a 68 through early 69. The 584 tail housing is a 65-70.
A-E=Jan-May
H=Jun
K=Jul
M=Aug
P=Sep
R=Oct
S=Nov
T=Dec
So, as you can see, it very clearly APPEARS to be built Oct 31 1968, which, normally would go into a 1969 car that was assembled sometime in Nov 1968. Did someone actually see this tranny come out of a matching numbers Corvette? Because if they did not, then I really think it came from some kind of an early 1969 model car.

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I finally have all the pieces, thanks to everyone's help. The VIN is correct 18S404327 translates as follows: 68 to 72 the trannys where stampeds with 1= Chevrolet, 8= 68, S= St.Louis, etc. As far as the other number P8MR31 translates as follows: P= Muncie, 8= indicates the model year not the calander year. So for a car in the 4000 serial number range October of calander year 1967 is about right. This also explains why there is not a A, B, or C letter after the number. As I found out M-22 have the lower main case boss drilled out and tapped for a drain plug. This is a fairly accurate identification method unless someone has drilled and tapped the boss on a non- M-22 trans. No I don't have a drain plug. But I known what I do have a M-20 or a M-21 68 vette trans.