A727
transmissions from their inception until 1966 have 19 splines on the
input shaft. Nonlockup
727 transmissions from 1967 onward have 24 spline input, and 29 spline output shaft
Lockup 727 transmissions that debuted in 1978 had 23 splines.
Not all 727 transmissions made after 1978 were lockup; specifically towing
package 727 transmissions commonly were nonlockup,
and would have the '67onward 24 spline input shaft. The A518
overdrive also has 23 splines. The output shaft has 29 splines.
A904
transmissions from their inception until 1967 have 18 splines in the
input shaft. Nonlockup
transmissions from 1968 have 27 splines.
Lockup 904 transmissions appeared in 1978, and have 26 splines. A500
overdrive transmissions also have 26 splines. The output shaft has 25 splines.