1969 Muncie 4 speed M20, M21 or M22

[David D.]

How do I determine which of the three Muncie 4 speeds that I have in my car? M20, M21 or M22 ??

[Rich P.]

Re: 1969 Muncie 4 speed M20, M21 or M22

From your profile, you have a 400 HP car that eliminates the M-22. Depending when you car was built they started coding 69's with the trans ID in the build date stamped into you trans it will end with an A or B. A is M-20 B is M-21. Also check to see if you have the metal tag bolted to the side cover. If you have it post the #'s and some one will decode it.

Rich

[David D.]

Re: 1969 Muncie 4 speed M20, M21 or M22

I didn't find any code on the case with an A or a B in the number. But it does have the metal tag you described and here is the code: 3950356

[Ronald L.]

Re: 1969 Muncie 4 speed M20, M21 or M22

Here is the definitive link:

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

follow the links and you can decipher.

You must look on the flanges and areas indicated to get casting numbers, casting dates, and the stamped in info off that trans.

All that really won't guarantee what is inside if it was changed or blown and someone replaced your original from a fleebay bucket of bolts

If it is original - this will be exacting...

[Rich P.]

Re: 1969 Muncie 4 speed M20, M21 or M22

Dave your tag shows M-20,

Rich

[Patrick N.]

Re: 1969 Muncie 4 speed M20, M21 or M22

Dave and Rich, this threw me off when I was looking into the same question a while back-shouldn't the Feb, 22 build date code end with an "A" for M20? Not sure what that mark is but it is not an M22 for sure.
Dave, do you have a sufix similar to this? (I have a 400hp M20 but 68')

Pat

[Rich P.]

Re: 1969 Muncie 4 speed M20, M21 or M22

Pat, if I remember correctly the suffix's did not start till mid 69 so you 68 would not have it. I found the tag info from the Camaro AIM. Here is what I copied:


3950356 is for RPO M20 with L48, L34, L35, LM1
3946797 is for RPO M20 with Z28 & L78
3950316 is for RPO M21 with L34
3946798 is for RPO M21 with Z28 and L78
3950318 is for RPO M22 with Z28 and L78


So the L-35 L-35 application that would match the L-36-L-68 in the Vetes.

Rich

[Patrick N.]

Re: 1969 Muncie 4 speed M20, M21 or M22

Thanks Rich, that makes sense if the sufix was started in 69.

pat

[Wayne M.]

Re: 1969 Muncie 4 speed M20, M21 or M22

Pat, if I remember correctly the suffix's did not start till mid 69 so you 68 would not have it.

Correct -- early '69 Muncies assembled starting October 21st 1968 would be the first to have the A, B or C suffix. ie. P9R21A.

[David D.]

Re: 1969 Muncie 4 speed M20, M21 or M22

Ok my casting number is: 3925660 I have a code of: P9P12 above the stamped in partial VIN code which matches my VIN on the car. There is no A, B or C after that code.

[Wayne M.]

Re: 1969 Muncie 4 speed M20, M21 or M22

Ok my casting number is: 3925660 I have a code of: P9P12 above the stamped in partial VIN code which matches my VIN on the car. There is no A, B or C after that code.

That makes yours Sept 12th 1968, about 38 days before they started stamping the letter suffix. Now 1969 model year is a strange bird, because of the extended Corvette production thru December 1969. So if yours had the suffix, the trans would have been assembled 12 months later. It gets really weird when you consider that there are potentially two 1969 model year transmissions with identical assembly stampings, after Sept 21 of 1968. eg; both P9R29A, except one was done in calendar 1968 and the other in '69. So you have to rely on the monthly VIN derivative stamping, or in the situation of late 1969, Muncie started to use 3925661 cases.

[David D.]

Re: 1969 Muncie 4 speed M20, M21 or M22

Hey Wayne,
So without the suffix A, B or C on this date code we have to rely on the metal tag attached to the case (3950356) to determine which one it is ....correct?

And if so, according to a previous post, makes my Muncie originally manufactured as an M20....correct?

I've owned the car only about a year and based on the new cast colored paint on the casing and obvious new gasket material protruding from the case in several areas it was rebuilt or at minimum had new gaskets installed not long ago and I have no idea what the specs of the rebuild might have been if it was rebuilt......

Thanks,
Dave