The Ford C4 and C6 automatic transmissions have been equipped in millions of production rear-wheel drive cars and trucks since they were introduced in the 1960s (C4 in 1964, C6 in 1966). They remained in production deep into the 1980s, when overdrive-equipped transmissions finally eclipsed them. However, the C4 and C6 remain incredibly popular with enthusiasts, racers, and restorers alike due to their simplicity, strength, and low cost.

Rebuilding either of these transmissions isn't overly difficult, but does require care, some specialized tools, and proper procedure to be followed...