General Motors option code
M21
M21: a General Motors factory option code reused for more than one part across 1964–1978 and 6 models — see the table for what it named each year, with installs and price where a source states them.
General Motors reused this code for more than one part over the years — read the "as named that year" column for what it meant on each row rather than assuming one meaning throughout.
6 models · 12 model years · 12 sources
Every sourced appearance
| Year | Model | As named that year | Price | Installs |
|---|---|---|---|---|
| 1964 | Chevrolet Impala SS | Four-speed close ratio (V8 series) RPO | Unknown | Unknown |
| 1965 | Oldsmobile Cutlass, 4-4-2 and Hurst/Olds | Transmission, 4-speed close-ratio floor-shift RPO | $188.30 | Unknown |
| 1966 | Chevrolet Chevelle and Malibu SS | 4-speed close ratio RPO | $105.35 | 5,012 Reported |
| 1966 | Chevrolet Chevy II and Nova | Four-speed close-ratio manual transmission (V8: 114-116-11800) RPO | Unknown | Unknown |
| 1966 | Oldsmobile Cutlass, 4-4-2 and Hurst/Olds | Transmission, fully synchronized close-ratio 4-speed floor-shift (includes Hurst competition shifter; with performance axle ratio only) RPO | $184.31 | Unknown |
| 1967 | Chevrolet Chevelle and Malibu SS | 4-speed close ratio RPO | $184.35 | 12,886 Reported |
| 1967 | Oldsmobile Cutlass, 4-4-2 and Hurst/Olds | Transmission, fully synchronized special-ratio 4-speed floor-shift, Hurst competition shifter (3.91 rear axle ratio and V01 required) RPO | $184.31 | Unknown |
| 1968 | Chevrolet Chevelle and Malibu SS | 4-speed close ratio RPO | $184.35 | 11,208 Reported |
| 1968 | Chevrolet Chevy II and Nova | 4-speed close-ratio RPO | $184.35 | Unknown |
| 1968 | Oldsmobile Cutlass, 4-4-2 and Hurst/Olds | Transmission, fully synchronized 4-speed floor-shift close-ratio, Hurst competition shifter (V01 and G88 or G92 required; G88 standard axle; N.A. with C60 or Y72) RPO | $184.31 | Unknown |
| 1969 | Chevrolet Chevelle and Malibu SS | 4-Speed Transmission - Close Ratio RPO | $184.80 | 13,786 Reported |
| 1969 | Oldsmobile Cutlass, 4-4-2 and Hurst/Olds | Transmission, fully synchronized 4-speed floor-shift close-ratio, Hurst competition shifter (G80, V01 and G88 or V02 and G92 required; N.A. with C60 or Y72) RPO | $184.80 | Unknown |
| 1970 | Chevrolet Chevelle and Malibu SS | 4-Speed Transmission - Close Ratio RPO | $184.80 | 11,830 Reported |
| 1970 | Oldsmobile Cutlass, 4-4-2 and Hurst/Olds | Transmission, fully synchronized 4-speed floor-shift close-ratio, Hurst competition shifter RPO | $184.80 | Unknown |
| 1970 | Pontiac Firebird and Trans Am | Close Ration 4 Speed Manual Transmission with Hurst Floor Shift (sales code 358), Formula 400 with Peformance Axle (368) RPO/UPC | $195.36 | Unknown |
| 1973 | Chevrolet Chevelle and Malibu SS | Close-ratio 4-speed RPO | Unknown | 1,685 Reported |
| 1973 | Pontiac Firebird and Trans Am | 4 Speed Manual Close Ratio Transmission (sales code 36H) RPO/UPC | $200 | Unknown |
| 1974 | Chevrolet Chevelle and Malibu SS | 4-speed close-ratio RPO | $219 | Unknown |
| 1974 | Chevrolet El Camino SS | 4-speed close-ratio (LS4 454 with F40 or radial tires only) RPO | $197 | Unknown |
| 1974 | Pontiac Firebird and Trans Am | 4 Speed Manual Transmission (Close Ratio) RPO/UPC | Unknown | Unknown |
| 1975 | Pontiac Firebird and Trans Am | Close Ratio 4 Speed Manual Transmission (sales code 37F) RPO/UPC | Unknown | Unknown |
| 1976 | Pontiac Firebird and Trans Am | Close Ratio 4 Speed Manual Transmission (sales code 38F), Firebird, Esprit, and Formula RPO/UPC | $242 | Unknown |
| 1978 | Pontiac Firebird and Trans Am | Close Ratio 4 Speed Manual Transmission RPO/UPC | Unknown | Unknown |
Every row traces to the source it links from on that model's own year page; this table only collects them in one place.