Join Date: Sep 2000
Location: Washington, Michigan USA
3831704 cases (1963) and 3851325 ('64-'65) cases used the 7/8" countershaft, although many have been re-machined and converted to the 1" countershaft which was used from mid-'65 on, starting with the 3885010 case. M-22's were the only 3885010 and 3925660 cases with drain plugs from 1965-70, but starting with the 3925661 case ('70-'74), all Muncies had drain plugs.
More M-22 trivia; a fine-spline (26 tooth) input shaft does NOT necessarily signify an M-22. There were seven different Muncie input shafts - all 26-spline inputs had 32-spline outputs, and all 10-spline inputs had 27-spline outputs.
This refers to original build specs - not many Muncies are still around that haven't been rebuilt at least once, and due to the high degree of interchangeability of the cases and internal parts across the years and models, it's possible to build almost any combination from parts (which rebuilders have lots of).
'69 Z28 Fathom Green