What year was the spline change? I have a final drive and driveshaft from an unknown year K100. How do I tell which I have. Is the difference in spline on the transmission side or the FD side?

I assume you are talking about the driveshaft/final drive being changed from 16-tooth to 20-tooth? That was February 1986.

To know which one you have, just count the splines.

Thanks. That is what I need.