My friend took my Sportsman 500 for a spin and it started pulling hard to the right... like the tire is flat but the tire is fine. Is that the u-joint? If it is, how hard of a fix is that? I don't want to take it to the shop because it will be there forever.

 

It could be a U-joint, but if he had it in 4x4 the hub could be locked. If it is, back up while shaking the handle bars back and forth.

 

I will definitely try that. what about CV joints... do they cause the pull to one side or the other when they are out?

 

JF is right, back up and it should unlock the front diff.

 

I am being told that if the fluid in the hub is low, it will allow that wheel's 4 wd to engage and thus the pull hard to the right happens. Sound right?

 

If fluid low and dirty can cause sticking problems on armature plate. If going into hub area REPLACE anyway(about 10 bucks) if not already bad WILL eventually wear and magnetize. U-joint rear driveshafts up to 98 models that are worn can cause erratic pulling,BUT since yours is an 02 model,has cv driveshafts and shouldnt cause hard pulling.