[Bobs_cat]

So I am kinda on the hunt for a torque converter for my car. But in my readings I have found that the c4's changed at some point (67 ish?), and apparently the spline count changed as well as a few other small thing. My transmission has C6 cast on the case, so I am assuming it is of the first generation. The thing I can't find out is what the spline count is on my transmission (I am at school 3 hours away, with no car, so no, I can't just go check), and different places have 24 and 26 spline listed, so im kinda at a loss as to what it should be. And more importantly, I am assuming 26 is stronger than 24, so if I end up having a 24 spline input shaft, how hard is it to change it to a 26?

 

[cardoctor]

I think they were 24 spline up to 1969, then 26. The 26 is stronger but you would have to change clutch hub inside trans to a 26 for a 1970' you can grab the input shaft and pull it out and count the splines, some rebuilders will update to 26 spline when rebuilding trans, just because its a 66 does not guarantee it's a 24 spline. You also need torque converter with correct splines. In 1971, Ford went to a 26/24-spline input shaft, meaning the torque-converter side is 26-spline and the clutch hub is 24-spline. so if your input shaft is 24 going into the trans you could just buy a 1971 on up input shaft and a 71 or newer converter to have the 24/26 set up.