With our '14 550 Sportsman Versatrak, the gear shift level moves to all positions and in "R" (reverse), there's no movement with the wheeler. Fewer times, there's a slight gear-grinding sound heard, but most of the time there's no grinding sound and the wheeler will not move in reverse; the P, N, L and H modes work as expected. This is all done with the engine running.

Any ideas as to why reverse doesn't work, or why the transmission won't shift into reverse?

 

Okay, BUMP... to the top.

Anyone know why this model's tranny won't engage into REVERSE, but will in every other gear (P,N,H,L)?

 

I would check linkage adjustment, you could unhook linkage and see if you can manually put it into reverse. Worse case is reverse gear is stripped out or broke. My guess would be shifter linkage. Any metal parts when you drain transmission oil?