
It’s long been believed that the first year for a full-size Chevrolet with a factory four-speed transmission was 1959. However, some late-production ’58s left the factory with four-speed transmissions. They were conversions, but conversions done at the assembly plant nonetheless. As such, these four-speed, full-size 1958 Chevrolets should be considered factory-installed.
Regular Production Option (RPO)No. 685 in the 1958 passenger car instruction manual dated Feb. 13, 1958, (illustrated on opposite page) shows the four-speed conversion on four pages. The conversion included a unique transmission and extension assembly, a floor-mounted control lever and bracket, specific control rods and adjustment; a four-speed transmission mounting; and a seal and retainer for the floor-mounted shift handle.
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