I have a 2001 Polaris Scrambler 500 2x4
It just started clicking/clunking/knocking whenever I am on the throttle.
I think it is coming from the rear somewhere but am having trouble telling where it is coming from.
it is a steady, click...click...click faster as I throttle more and slower when slower.
Any help or ideas would be greatly appreciated

sounds like mine.....my axle (castle nuts) keep comming loose and make a clicking sound wile riding.

When my polaris did this, it was a gearbox problem...

lift your rear off the ground and see if the castle nuts are loose

your wheel nuts could be loose and you can't see it (like mine blush) made a hell of a clicking sound

check all nuts/bolts associated with the rear drive system. the problem will be somewhere along the rear axle, otherwise its a gearbox issue