4 Speed Transmission Identificationby Rob Wagner
General Motors, Ford and Chrysler equipped their vehicles with numerous types of four-speed, manual and automatic transmissions. Four-speeds were usually limited to pre-2000 vehicles.
Ford and General Motors equipped vehicles manufactured from 1957 to 1988 with the Borg-Warner T10. This transmission was available in a cast-iron case, and later an aluminum version. The four-speed featured nine-bolt covers, and 36-tooth synchro rings. The casting number was T10 plus two numerals, or "13-04."
GM muscle cars manufactured between 1963 and 1974 were frequently equipped with the Muncie M21 and M22 four-speeds. The case was made of aluminum, with a seven-bolt cover and 36-tooth synchro rings. Trucks manufactured from 1948 to 1967 used the Muncie SM420 version; it featured a cast-iron case and non-synchronized first gear. Trucks manufactured through 1991 used the SM465 model.
New Process four-speed manual transmissions came in three versions. The aluminum or iron-cased 440/MY6 helped power 1981 to 1987 trucks, and featured a non-synchronized first gear. The low-gear 435 was found on 1964 to 1972 vehicles. The casting numbers starting at C-9, followed by four digits.
Ford's AOD, four-speed automatic transmission was used by Mercury, Lincoln and F-Series pickup trucks. It featured a 14-bolt pattern on the cover, and weighed 150 pounds.
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