M22 transmission casting no. for 65-67 years

[Anthony S.]

Members, what is the casting on the transmission for M22 version across the years 1965 - 1967 cars? Would the casting # for M22 be the same as for M20 or M21 versions?? I.E, only way totell M22 is by engine stamp pad? Thanks Tony

[Clem Z.]

Re: M22 transmission casting no. for 65-67 years

try here. http://www.5speeds.com/muncie.htm

[Tom P.]

Re: M22 transmission casting no. for 65-67 years

ALL Muncies of the same year used the same main case, thus, they all had the same casting number.
The ONLY difference between an M20, M21, M22 are the internal gears.
The ONLY way to positively know if a Muncie has M22 gears inside of it is to remove the side cover and check the tooth angle (M22 gears have less angle on the teeth).
REGARDLESS of ANY code, ANYWHERE on the car, engine, tranny, that does not guarantee that the tranny has not been rebuilt in the past with different gears.
I've been rebuilding 4spds (mostly Muncies) for 45+yrs, and I cannot count the number of trannys I've put together with a mixed combination of parts.
Here is a comparrison between M22 gears (top picture) and M20/M21 gears.

[Wayne M.]

Re: M22 transmission casting no. for 65-67 years

Tony -- Tom gives good advice. I'd go so far to say that after 45+ years, very few Muncie's have their original internals.

No M22's had special maincase casting numbers. There's that Canadian '65 L78 tanker ordered to race; the factory installed an M22, written up in A.Colvin's '65-9 Chevy book. the casting number was routered off (probably to signal the unit was not like the others).

The A, B, C suffix stamping to identify gearset didn't start until October 21, 1969. As for going by the engine stamping, 1967 is the only C2 year that you could deduce the trans by the engine code, only because that trans was mandatory for L88 [IT code].

[Ray K.]

Re: M22 transmission casting no. for 65-67 years

Tony

Original Muncie M22's were supposed to have a lubricant drain plug tapped into the boss on the case, where as M20's and M21's did not have this feature. Any evidence of this on yours?

Ray

[Eric D.]

Re: M22 transmission casting no. for 65-67 years

The A-B-C ratio code started October 21, 1968 for use in 1969 model year cars...

The drain plug on early Muncie's works, 1970 model year Muncie's and later all main cases were drilled and tapped for fill and drain plugs...

The only problem with the early Muncie drain plug is, it's not too hard to put an empty case in a drill press and drill and tap a drain plug, its only 1/2" pipe thread... And I've tapped a bunch of them, Tom probably has too..

Early M-22's built at Muncie used a different magnetic drain plug than 1970 and later Muncie's...

Hope this helps... Eric

[Tom P.]

Re: M22 transmission casting no. for 65-67 years

The A-B-C ratio code started October 21, 1968 for use in 1969 model year cars...

The drain plug on early Muncie's works, 1970 model year Muncie's and later all main cases were drilled and tapped for fill and drain plugs...

The only problem with the early Muncie drain plug is, it's not too hard to put an empty case in a drill press and drill and tap a drain plug, its only 1/2" pipe thread... And I've tapped a bunch of them, Tom probably has too..

Early M-22's built at Muncie used a different magnetic drain plug than 1970 and later Muncie's...

Hope this helps... Eric

That is exactly correct, I've installed drain plugs in MANY, MANY Muncie cases. I've even done it IN THE CAR a few times. Once I get the hole drilled/tapped, I use 2-3 long stick cotten tipped applicators to pull out the alum cuttings. The oil in the case will help wash the metal cuttings toward the hole.
I used to buy 2-3 magnetic drain plugs at a time for $5-6ea from my Chevy parts guy. Several years ago, I discovered a source for magnetic drain plugs (with the same head marking as the ones I bought from Chevy parts). I bought a box of 100 @ $.50ea!!! I'm down to about 75 now.