I did a search and came up with nothing, 2002 sportsman 500HO
I was climbing a sand pit wall in low range and the AWD button in AWD as the quad slowed down the rear wheel were spinning but the front weren't engaged and it came to a stop ( rears still spinning), I backed up about 2 feet and started forward again the fronts engaged for about 5 feet then disengaged again, I did this about 3 times and it did the same thing everytime. My question is - is there a RPM limit when in low range for the front wheel engagement?
Ithought I read somewhere that they disengage after 3000 RPM but can't be sure.
Don

 

Try this as seems like grounding is the cause of a lot of awd problems other than mechanical.
Plus wouldn't hurt to do a hub fluid change if you haven't done it lately and see how it works. If this or grounding doesn't help,could be a mechanical problem in the hubs,usually armature plates. Haven't read where they disengage at 3000 rpm,but the limiter in the speedo keeps the hubs from engaging at high rpm which is around the 3000 rpms you mentioned so damage to the awd won't happen.