I have the same with my 2006 Hawkeye. Have electrical signal at the front diff so I suspect my issue is the knackered seals on central front diff letting most of the drive oil out! Driven it in 2wd mode for a year but badly miss the fwd in the winter. Just ordered new driveshafts and bottom ball joints, wishbone bush kit and front diff rebuild kit. Not cheap but selling it and buying again is way more expensive. Once all the parts arrive will tear it down and replace everything together.
Btw, got everything off eBay between wales quads in Swansea and various suppliers in USA and Canada.