Identifying Saginaw 4-speed or a Muncie 4-speed on a 1967
Short answer: Quickest tells: a Muncie is aluminum with the reverse lever in the extension (tailshaft) housing; a Saginaw is cast iron with the reverse lever in the side cover (both have 7-bolt covers).
In first-gens, V-8s used Muncies and OHC-6 (1- and 4-bbl) used Saginaws — though a few 4-bbl OHC cars got Muncies (assembly-line goofs). The M-22 “rock crusher” (close-ratio only, identified internally by its straighter gear-tooth angle) was not installed in early Firebirds; the M-20/M-21/M-22 differ in input shaft, cluster, and gears. M-21/M-22 first gear is 2.20. Check your two-digit axle code for ratio.
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Content last modified: June 13, 2026 at 10:06 am
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