Coarse Thread Drive Shaft
Used in upper crank assemblies.
The crank assembly gears and mechanism ride on this drive shaft. The drive hub extension tube threads onto the second set of threads of this shaft.
Dimensions are 3 3/4" long and 5/8" diameter at it's widest point. The rear pin hole for the toothed sprocket sits at 7/8 of an inch as measured from the rear to the center of the hole.
Here are examples of drive shafts with damaged threads.
The threads at the end of the drive shaft are coarse thread for the 5/8 nut.
Part number 4751B3522