My 69 Z is supossed to have a M-22....I have looked as close as I can at the gearbox with it in the car and these are the numbers on it

Tailshaft section : 3857584GM

Main Case: 3925660

US Patent no 03088336
General Motors Corp

On the main case flange it reads my VIN 19L5XXXXX P9A24B

(Sorry for xing out the VIN...I always see people doing this so I figure you are supossed to

Can you tell by these numbers what gearbox I have ? My Norwood Z/28 has the 3925660 and it is an M-21....is this also ?

The last letter of your P9A24B stamping shows it to be an M-21. A=M-20 B=M-21 C=M-22
The rest of your numbers look fine. Looks like you should have an early Feburary build date. Hope that helps.
Doug

The tail shaft section is correct for a Z/28 and so is the main case. They do not tell you what type of gear set they are though. What determines the gear set is having a look at the input shaft to see how many rings are on it. No rings is an M22 input, one is an M21, and 2 is an M20. You can also tell be the build date which are the numbers that are stamped along the mid plate on the passenger side of the case.

You said they were P9A24B which decodes to:

P = Muncie
9 = Year of Build 1969
A = January
24= Day of the month
B = M21

With that being said, I would think this is a non matching trans for your car since you state it's an M22 car. What month was your car built on? It should be noted on your Trim Tag as a 2 digit code followed by a letter. (i.e. 06A)

Cheers

What makes you say that it's suposed to have an M-22? Is that what you were told by previous owner?
You also said that your VIN is stamped by the date code, so unless it's been re-stamped, it's the original M-21.

http://www.dandltransmission.com/muncieratio.html might be of some help.

Dennis ,
The owner has passed away. He bought a lot of cars from Clipinger Chevrolet down the street from his home. All these cars were sitting on his property when he died and his son the executer sold two then ran a bulldozer over the rest...the only cars that made it out alive are mine and a 57 chevy Bel Air..the rest are scrap metal and the son has been insitutionalized..true story and a deaper meaning to the word "survivor"..so to get to the point I think you are right, he said it was an M-22 but he was obviously mistaken..wish it was an M-22 but that's OK..this car has everything original on it including the air pump , I am still thrilled about having it.
Appreciate everyone's feedback.

I think alot of people have been confused of the use of M-21 & 22's due to the same close ratio gearing. If you had the M-22, you wouldn't have to ask, because you would be aware of the obvious aggressive meshing noise. It is pretty much unmistakable compared to any other tranny.

[ 12-16-2004, 02:21 PM: Message edited by: sicsD8 ]

ChevyThunder,
Have you looked on top of the gas tank for the chassis broadcast copy?

Doug ,
I have not but believe me I am anxious to do so . I may try and look tomorrow..if I can get out of going to San Francisco for Christmas shopping with the girlfriend:)