"65" Muncie C-22 Heavy Duty Tranny

[Doug #42330]

I think I may have one of the rare Muncie C-22 Heavy Duty 4 spd transmissions in my 65. It has a drain plug on the side and the book says that only the C-22 had the drain plug. Or maybe I am reading it wrong. Is there any way to tell for sure if it is a "22" or not?

Doug

[Joe L.]

Re: "65" Muncie C-22 Heavy Duty Tranny

Doug-----

The drain plug is not a positive indication that it's an M-22. Generally, the factory only used the drain plug cases for M-22's in the 1965-69 time period. However, I'm sure that they may have used a case with drain plug for other variants on occasion. Other possibilities exist, too. First, the drain plug could have been added by some previous owner or rebuilder. This was a fairly common practice once-upon-a-time.

Second, the transmission could have a replaced main case. Of course, that would be ruled out if the case has an original VIN derivative stamping.

One other thing to check for: I believe that all 1965 with M-22 used the standard 1965 maincase cast GM #3851325. This case used a 7/8" countershaft bore. All M-22 transmissions used a 1" coutershaft bore. So, either the 3851325 maincase was used with an enlarged countershaft bore and with the case casting number machined off OR the 1966 main case, GM casting #3885010 was used. If your maincase has the 3851325 casting number on the passenger side, I doubt that it's an M-22. If it has a machined off casting number or a 3885010 main case (and is known original to the car), then it's very likely an M-22.

The only way to positively ID the transmission is to remove the side cover and inspect the gears. However, the M-22 makes a very noticeable whine and that, by itself, should be enough to discern its identity.

For the car to have an M-22 under any circumstances, it would have to be a VERY late car (like no earlier than May, 1965) AND be equipped with either the L-78 or L-84.

[Patrick T.]

'65 Muncie M-22 Heavy Duty Transmission..

Here is a picture of an M-22. Note the helix angle of the splines (gear teeth) is a low 21 degrees from horizontal as opposed to 37 degrees on a M-21. PT

[William C.]

Re: "65" Muncie C-22 Heavy Duty Tranny

All muncies with the '661 case used the drain plug. Start with the casting number and go from there.

[George C.]

Re: "65" Muncie C-22 Heavy Duty Tranny

Doug,
As Joe said the M22 makes a noticable whine. That is putting it mildly, the transmission became known as the M22 Rock Crusher, for good reason. It was tough as nails, and had a very unique sound to it, call it a whine or a roar.

George

[Wayne M.]

My neighbours call it annoying

or sometimes "showoff". Putting 4.56's in soon so I can troll through the streets even slower at 1st gear's whiniest (around 2000 rpm).

[Mike M.]

Re: My neighbours call it annoying

wayne: i like your attitude. you can cruise our neighborhood anytime. mike