not really a tech question, but more curiosity.

is it true that when in 4wd, 1 front and 1 rear wheel MUST spin at EXACTLY the same speed and distance?

i've noticed that when i'm in 4wd (either off road or on wet roads), that my inside rear wheel carries on a bit. similar characteristics to having a locker fitted. (inside wheel skips/skids)

i guess this is why they call it wind up.

One front wheel and one rear wheel the same speed?  No.  The sum of right rear plus left rear must equal the sum of right front plus left front.  Or, the way we usually say it, is the front and rear driveshafts are locked together and must turn the same speed.  The binding on dry pavement is the different radius, in the turn, between the front of the truck and the back of the truck.

Stay off the dry pavement in
4WD or you could snap alxes
or U-joints, crossing a paved
road or a short (50ft) straight
drive would probably be OK
but I try to not take any chances

Wild

Ya right, you believe that coming from a guy that has a turbo and 4wd, he prob. trys to keep up with the subaru's and the mustang's on the way up to Big Bear mountain  

As far as I now, "Wind-Up" or "Axil Rap" is something only leaf springs do.  When the tires grab and a lot a torque is applied to the axil, the axil will twist (wind-up) the spring to the point it has enof power to break the tire loose and the spring lets go.

Easy way to break and axil.  

That one nice thing about coils, don't have to worry about that.

The axle shafts still wind up, just
the housing doesn't move around
as much