Bought a 2002 Prairie 300 with some drivetrain issues. Have all 4 wheels off the ground.

If I rotate a front wheel they both spin as well as the driveshaft back to the transfer case.
If I rotate a back wheel both back wheels spin as well as both front wheels. If I Spin a back wheel hard is slips like splines are stripped. Question, is it the hub or axle that usually strips first?

And is there a way to out the ATV in 2WD ?
Looks like there is a cable that is broken off the rear differential, what is that for?

Thanks.