AS\s said. Also while it is loose it might help if you spin the rear wheel to help it center up if that is the issue. Especially if the click is like 4 times faster than the wheel is turning. Good thought GL.Loosen and re-tighten the bolts that hold the final drive to the swing arm.
How about this CAREFULLY. Put the bike on the centerstand while it is acting up. Start the engine and duplicate the speed just spinning the wheel. Does it make noise freewheeling like that? Apply some load by applying brake. Does it click then? That brings up another question. Driving down the road with the bike clicking apply slight brake. Does it stop clicking when you apply brake. Apply brake and use some throttle to overcome the brake. Any better. Don't overlook what gl mentioned. If the final drive is not entered it might click where the spline meets. That is any easy try. Loosen 4 bolts a few turns and sping the wheel or start the engine to spin the wheel. Tighten back up. Like Dave B says, Easy stuff first.I did lube the splines where the hub with the pins mate with the splines on the final drive. When it is cool, it doesn’t make noise. After a few miles, I can hear it when I am going super slow. I don’t hear anything at faster speeds. I guess I have to pull the rear wheel again. As you all know, it isn’t a picnic doing that. I use the method where you pivot the hitch and all the trunks up out of the way. I used the stethoscope with it on the center stand and in gear running and it isn’t the brakes. It also isn’t as noticeable unless you are riding it.
In the final drive at the opposite end of the drive shaft from universals- replaced several final drives of friends bikes due to lack of lubrication over an extended period of time... Last one I did required drive shaft and rear end replacement due to excessive wear... Honda's Moly Paste will work fine back there... I would lube it at every tire change or at least every other tire change on a 1500...which driveshaft splines? the ones in the U joint or the ones on the Final Drive? the pins? cant see how they would click? they are a pretty solid fit in their holes and the pins are chrome plated and have to be HARD . I took mine apart and they were dry dry dry with rust in the holes. never enough time to do it right the FIRST TIME.... but ALWAYS time to do IT AGAIN . when everything is done... there is ALWAYS ONE MORE THING TO DO.