I'm working on my neighbor's Husqvarna 4421G side-by-side. I think the year is 2007. The rear wheels won't pull but they do spin when I have it up on jack stands. With the transmission in neutral, I can turn either rear wheel by hand and neither the other wheel turns nor does the drive shaft turn. Parts diagrams are sketchy and parts are largely unavailable, so I'm reluctant to tear into it without some idea of where the problem actually is. Anybody have any experience with these?