slip yoke length?

[swing69]

for a 904, I have a few old driveshafts kicking around. I noticed that there are some long and short ones. (no measurements on hand).

What gives? I would have thought all the 904 slips would be the same. can someone tell me when they would used 1 vs. the other?

 

[fishy68]

I've noticed that with both 904 and 727 yokes. I believe most of the time they all have the same amount of spline length inside. Some just have a extra 1/2" or so of non splined area on the inside. Whey they did it I have no idea