I like to see the axles splines fit past the inside edge of the spool splines. there are some spools that are splined all the way thru so that won't work on them,the ones that I have measured that are not full lenght splines have 1.5 to 2 inches of splines on each side with about a two inch space between them on the inside. I hope that makes sense I have several Strange and Yukon 35 spline spools for a 8 3/4 that I could measure in the morning to make sure, if needed. let me know if needed