I have the granny gear 4 speed , and want to remove the speedo drive gear to see what is going on in there.

The coupling has a 15/16" hex. I tried to unscrew it, but it is very tight. It moved, but it took a lot of force to just budge it a little.

Before breaking anything, I thought I'd check here. Is it OK to unscrew that part to get to the drive gear?