4-speed wide / close ratio

Years 1966–70 Models 1 Factory citations 2

Also described as 4-speed manual wide-ratio / close-ratio, floor shift

Documented applications

1966–67 Confirmed

4-4-2
1968–69 Factory-verified

M-20 "4 Speed Fully Synchronized, Wide Ratio, Floor Shift" / M-21 "4 Speed Close Ratio Synchronized, Floor Shift"

GM Heritage factory kit — 1969 Oldsmobile 442 Info Kit, p.247.
1970 Factory-verified

Factory list: M-20 "4-Speed Fully Synchronized - Floor Shift" / M-21 "4-Speed - Close Ratio Fully Synchronized"

GM Heritage factory kit — 1970 Oldsmobile 442 Info Kit, p.229.

This page aggregates every documented appearance of M-20 / M-21 in the Oldsmobile reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.