ok so i found out that detroit makes a locker for 34 spline 9.75 axles. i have the 9.75 in my 01 f150 but dont know what spline shafts i have, is there any way to tell without pulling them out?

Look on the differential for a metal tag. Take all the numbers off of it and go to a ford truck site and have it decoded.

Most likely it is a 34 spline unit. Thoes axles only came in the '97-'03 F150's with the 5.4L in it.