Weird 4x4 Problems

I have a 99 z71 sportside and in the last little while noticed some weird stuff. I've notcied at times that if I happen to take off and have the wheel cranked to the left or right and the back wheels spin a bit, wether it be on snow or sand, that it almost feels like the four wheel drive is engaged ... I get a jerky motion happening which I feel in the steering wheel identical to what you would feel when you have the four wheel drive engaged when you are on dry pavement ... anyone have any ideas on this?

Thanks in advance.
V

You may have a limited slip rear differential which is grabbing. Try changing the diff lube and use a lube specifically intended for limited slip rear ends. I think the dealer may sell an additive to add to the new lube that may help.