Why It Matters
A wide-ratio four-speed was standard; M21, the ZR1 special close-ratio unit, and M40 Turbo Hydra-Matic were alternatives. Case, stamp, date, ratio, shifter, linkage, drivetrain compatibility, and paperwork must agree.
Also Known As
1972 Corvette four-speed1972 Corvette M211972 Corvette Turbo Hydra-Matic