Well, you know what you say about the internet... you can't believe everything you read!

I realize these last few posts are a sidebar or tangent from the usual build, but what I'm finding is interesting nonetheless. Who knew that so many places list different spline counts for the same differentials? Or that the 2015+ Mustang GT and 2015+ F150 ring and pinions are interchangeable if you don't have any towing package that bumps the axle up to a 9.75" ring and pinion? Or that even truck guys on forums don't know what size differential they actually have because they only think of the number of bolts matters (now some realize that was an easy identifier in the past)?

Anyway, I stopped by a local spline and gear manufacturing business that turns out splines and hobs some Boeing parts. They confirmed that the spline pattern should be a standard 24/48 involute profile which got me thinking. What kept bugging me was that with a given diametrical pitch and pressure angle, you can't just increase the diameter without increasing the spline count. Well, that made me recount the splines on the Mustang GT stock pinion and flange. I thought I mis-counted because I read 30 spline everywhere, but there are 31 splines now!
Long story short, I ordered a 2015+ F150, 31 spline flange that seems to fit both the Super 8.8" and 9.75" differentials. Once that arrives, I can confirm.