Okay I have been all over here, and cannot find what I am looking for. I am trying to decode my '72 4SPD... The numbers are as follows,
PIM28C
and the casting number is 392566 and the bell housing number is 3899621. Any input... DEEPLY APPECIATED!!!

 

http://www.nastyz28.com/chevy-manual...tification.php


go here hope this helps

 

or here:

http://www.5speeds.com/muncie2.htm

Google "muncie decode" for more reading.

 

It would appear you have a Muncie 4 speed, (P) dated August 28 and model year 1971 (1M28) and it's an M22 "Rock Crusher" (C).

But I didn't see your casting number listed, maybe it's missing a 1 on the end?

Casting: 3925661 Years: 1970 - 1974 Ratios: M20 2.52 1st , M21 2.20 1st, M22 2.20 1st

cc

 

CC:
Thank You for the extra set of eyes! And spelling it all out, I am a little suprised to have the "rock crusher" behind a numbers matching 200hp 350 1972 car/eng! It also has the 10 spline input shaft as well and all the rest of the numbers seem to bear out that it is an original to the car unit. My casting number that I found is (392566) on the trans casing, I do see what You are talking about, I am a number short... Perhaps I just missed it! I will go back a double check it, another is on the bell housing 3899621, telling Me that it has an 11"? Thanks again for Your interest in helping Me.. -Bob

 

There should be another number,and yes,the 621 is the 11" setup.
Does the trans have the drinplug on the bottom of the RH side,and no rings on the input shaft?
A very u8nusual car for a m22 to go into,but maybe it is a error,or they were short,so grabbed what was ready to not slow up the line.

 

Your VIN should be on the case also. Same numbers that are on the engine pad. I think the are on the passenger side front edge sideways but I could be way off on that. It's been a long time since I looked mine up.

And you are very welcome. I really enjoy being able to help whenever I can. I have all these manuals and books so it's good to be able to put them to use and not just for myself.

cc

 

The trans does have the drain plug on the pass. side and is horizontal (sideways) down and forward the fill plug. Yes I did omit the last number on the casting number, it reads: (3925661) I have been back underneath the car numerous times and all the numbers that I had posted check out including (PIM28C) showing that it is a m22, and the trans bell housing (3899621) showing that it is for a 11" flywheel. I cannot answer yet about the the rings on the input shaft (not out of car yet)
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It would appear you have a Muncie 4 speed, (P) dated August 28 and model year 1971 (1M28) and it's an M22 "Rock Crusher" (C).

But I didn't see your casting number listed, maybe it's missing a 1 on the end?

Casting: 3925661 Years: 1970 - 1974 Ratios: M20 2.52 1st , M21 2.20 1st, M22 2.20 1st

cc
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The production date that CC posted for Me (above) bears out the correct build period with the vin production numbers (502004) so I am very close to positive this is a numbers correct trans. However I have look every where I was told to look and there is NO vin numbers stamped anywhere on the trans... Is it possiable that not all trans. where stamped w/vin numbers??? I have confirmed that I do still have the numbers correct engine.

 

All I can find in the Tech manual is that the VIN derivative is stamped next to the production code number which is P1M28C.

cc

 

CC; There is only one number there (PIM28C) and it is centered in that (area) spot. I'm kinda thinkin' with Vettesbydesign... this M-22 was a boo, boo! Thanks again, -Bob

 

My only problem with this is the 10 spline input shaft. I have an early build August car and it has a 26 spline input shaft. It is a 72. The car was built the second week of August so the trans should have been built before yours and it is a 26 spline. Mine has my VIN number on the side of the trans also. This may have been swapped into the car. If the trans is truely built in August of 71 it should be a 26 spline input, unless this is a freak car which could be possible.

 

Gordonm, his car is a year earlier than yours. It is a 71 model year car built in August of 70.

cc

 

Am I reading the other posters correct saying the trans was built in August of 71??. The trans should have been built in June July or August of 70. Correct???

His VIN is 502004 which is for a 72 car

 

Correct, the date code on the trans is a model year code not a production year code.

However, this trans was built August 28, 1970.

cc

 

That would indicate the transmission is not correct for his car.

cc

 

Yes I just looked at my number and it is P2M09A, but what about his VIN number with a 5 in the digit. That would indicate a 72 car. Mine is 500185

 

Yeah, mine is 509472 and P2T07A.

Somehow I missed the fact that he had a '72 base small block. Someone has swapped the transmission for a '71 M22.

Seems like I read there were no M22's in '72.

cc

 

Okay, the trans will be coming out next week, so until then I went ahead and bought a clutch pack kit from Autozone by year and engine size. I was given a 10.4", 26 spline set up. Then I get to looking at the numbers on the bell housing (3899621) that decodes to an 11" set up... So now I go to NAPA and buy the clutch pack that's 11" this set has the 10 spline set up, so at this point I will not know until it comes apart to be sure which one is really in there, I wouldn't think there would be a 10.4" setup inside a bell housing that is marked otherwise? IS THERE AN 11" CLUTCH SETUP W/26 SPLINES? However the (P1M28C) number still stands as being an M-22? Belive Me Guy's I am just as anxious to find out this Myself! Say tuned... film at eleven!!!

 

Yes there are plenty of 11 inch 26 spline setups. That is more common then the smaller clutch. It does decode out to be a 71 M22 but lets see when it comes out. I run an 11 inch 26 spline in mine. Beleive me the guys at Autozone are pretty clueless when it comes to older parts.

 

You know I have to wonder if the PO set this up with a different engine and transmission, kept the engine and stuffed the original one back in.

It makes sense to put an M22 behind a 383 stroker or something along those lines.

cc