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Posts tagged Mustang Top Loader

Ford Mustang Top Loader 4 speed Manual Transmission

The Ford heavy duty top loader 4 speed transmissions were, and may still be, the toughest and most reliable manual transmissions ever built.

How have they changed over the years?

The early (1963, 1964) top loaders had a small input shaft with 10 splines and a 15/16″ diameter.  The output shaft on these early transmissions had 25 splines.

In 1965, these early 4 speeds were upgraded to a 28 spline output, while the input remained the same.

During the 1967-1968 era, Ford had to come up with a strong, bullet-proof 4 speed for NASCAR competition.  This became the NASCAR Big Block 4 speed transmission and it had an input shaft with a 1 3/8″ diameter and a 31 spline output shaft.  A select few of these transmissions were used in NASCAR grand national racing.

The NASCAR transmission was also used in 1969 and 1970 Boss 429 cars.