[RichardJ]

You have no wheels and no drive shaft?
Unless you have a brake dragging, whether it has posi or not, when you turn the pinion yoke, both drums will turn the same amount.
Mark the drums so you can determine when they have both made ONE complete revolution and count the number of turns it takes on the yoke.

I've always done it this way with tires and drive shaft in place. Chalk the tires and the ground next to them. Jack the axle up in the center, chalk the drive shaft and count the turns needed to bring the tires back around to the mark.
I've always thought it was easier.