Pinion spline count?

[440Cuda]

I've got a 70 383/4spd Cuda (soon to be 440/6) with the stock 3.23 suregrip in the original 489 case (large yoke) and want to change the gears to 3.91 but need to know if the pinion gear has a fine or coarse spline.  How can I find out without pulling the yoke?  Any help would be greatly appreciated.

Thanks

440Cuda

[Chryco Psycho]

I can`t think of any way to find out without removing the pinion nut which releases the pressure from the brgs & crush sleeve  but you won`t have to remove the yolk just pull the washer out with a magnet & you can see the spline. Strange has both yolks available, fine or coarse spline