Coarse Thread Drive Shaft
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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.
It’s important to replace this drive shaft with the same end threads, fine or coarse, and confirm the drive hub thread measurements.
Over the year changes occurred to the crank mount plates, and depth of the shaft bushings. The drive hub extension tube needs to engage with the maximum number of threads on this drive shaft. Not confirming the length can lead to only a few threads engaged, then failure.
Measured from the bottom, the drive shaft threads start at 1-7/8 inches, and extend to 2-3/8th inches.
The threads at the end of the drive shaft are coarse thread for the 5/8 nut.
Looking to add a coarse thread nut to your order?
Part number 4751B3522