Guide to Muncie M20, M21, and M22 FourSpeed...
Aug 07, 2018 · The M22 Rock Crusher would come later to accommodate the heavy twist of Chevrolet's bigblocks in the mid1960s. The M20 and M21 transmissions produced from 1963'74 are easy to identify in both wide and closeratio units. The M22 to come later in 1967'74 is also a closeratio unit, but much stronger than the M21, with a higher torque ...