Trying to ID my Munci transmission

[sincro]

I have a 1965 Coupe and I am trying to identify the 4 speed transmission that is in it. It is a Munci but I can't tell if it is a M-21 or an M-22. The input shaft does not have any rings on it and it has a drain plug. According to the books I have, it is a M-22 but they didn't come in 65 models. The tag # is 3857580.

 

[JohnZ]

If the part number tag is original to the transmission, it identifies a 1965 wide-ratio (M20) used with the 250hp and 300hp engines; from '63-'65, no grooves on the input shaft identified the same usage. Chances are the drain plug was added during a rebuild - that was a common modification.

What's the casting number on the main case (above the patent number)? What's the VIN derivative stamped on the vertical rib at the rear of the main case?

 

[sincro]

Thanks for the information. The casting number is 3851325 and the stamped number that you described is P0116. There is a stamped number on the shifter side that is S1007542. I sure appreciate any information you might be willing to share.

Thanks

 

[Craig -1965]

Hello,

Forget the tag for now, if your transmission has a fill and drain ports than it's an M-22 I have one in my 65, and it's the only M transmission with both ports....... Unless the previous owner was tired of sucking the oil out and added the drain then the tag may have some merit.

 

[JohnZ]

Thanks for the information. The casting number is 3851325 and the stamped number that you described is P0116. There is a stamped number on the shifter side that is S1007542. I sure appreciate any information you might be willing to share.

Thanks

The casting number confirms a '65 main case, the VIN number is for a '65 Corvette built January 21, and the "P"-stamp says the transmission was assembled at Muncie on January 16th. It's an M20.

 

[JohnZ]

Hello,

Forget the tag for now, if your transmission has a fill and drain ports than it's an M-22

Nope. His transmission was built in January, and the first M22's weren't built at Muncie until late April (and none went into Corvettes - they only went into Chevelles in '65). Many rebuilders added the drain plug as a convenience feature.

 

[Craig -1965]

Hello John,

Looks like your correct, I didn't get out my Corvette black book, another way to tell an M-22 (without the book) is the incredable high pitch wine that come from the square cut gears, unless you have side pipes and then you can't even hear the radio or much else..... which is not a bad thing.

Have a good one.

 

[Tom Bryant]

Not exactly square cut but definately a much lesser angle than the M20 or M21. This is an M22. As you said they have a loud whine. I had an original 1970 El Camino SS 454/450 hp LS6 with the M22 in 1972-1974 and several people told me that my tranny was going out. :L

 

[sincro]

ID of my transmission

Thanks for all of you comments and information. The car isn't running right now so I can't tell if it has a high pitch wine but the gears inside don't look like the photo of the M-22 that was attached to one of the replies. I hope to get the engine back in this weekend so I should finally be able to drive it with a week or two.

Thanks to all who replied.