Question about spline count

[Matt68]

1973 Plymouth Barracuda. Originally a 318 car. My question is, should I have a 24 or 19 spline 727? Is there one count that is typically in a '73 Barracuda? Trying to buy a new Converter and need to know the spline count hopefully without having to drop the trans.

 

[marksmopars]

23 spline was small block application, 19 spline was big block as it was perceived to be a stronger design for th e larger amount of torque produced. Hope that helps

 

[Matt68]

@marksmopars you do mean 24 spline, not 23, correct? What's the difference in 23 vs 24 spline applications? How can I know which one I need with dropping the trans?

 

[Vaanth]

NOTE: Assuming no changes to original input shafts in the transmission in the following listing.



The 1962-1966 A727 Torqueflite input shaft has 19 splines.

The 1967- 1977 A727 Torqueflite and 1978-1991 A727 Torqueflite with non-lockup converter input shaft has 24 splines.

The 1978-1990 A727 Torqueflite with lockup converter input shaft has 23 splines plus a smooth machined area without splines at the nose of the shaft.

The A518 Torqueflite with overdrive, that replaced the A727, input shaft also has 23 splines.



The 1960-1967 A904 Torqueflite input shaft has 18 splines.

The 1968-1977 A904 Torqueflite input shaft has 27 splines.

The 1978~2002 A904, including A998 and A999, Torqueflite with lockup converter input shaft has 26 splines plus a smooth machined area without splines at the nose of the shaft.

The A500 Torqueflite with overdrive, that replaced the A904, input shaft also has 26 splines.

 

[marksmopars]

@marksmopars you do mean 24 spline, not 23, correct? What's the difference in 23 vs 24 spline applications? How can I know which one I need with dropping the trans?

View attachment 136622

I think Vaanth put it as clear as possible, it appears he has more information on this than I do so I bow to his expertise and offer my thanks to him for the information.

 

[Matt68]

@Vaanth last question; does converter diameter matter at all? I see 10", 11" 12"?

 

[Vaanth]

@Vaanth last question; does converter diameter matter at all? I see 10", 11" 12"?

In regard to the input spline size, the converter diameter does not matter.