how do u know if your 4x4 really works???

what would be a true test to see if your 4x4 be it 4 hi or low is really working.would it be to jack all 4 tires off the ground put it in 4 hi give it gas and see if all wheells are spinning????cheers.

Check out this post. (http://www.automotiveforums.com/vbulletin/showthread.php?t=767186)

As Delcoch pointed out read that post and do some searching.
The old crow hop test. Is a fast and easy way to check it.
Drop it in real 4W high or 4W low and make a sharp turn on dry payment.
If you have a crow hop or 4W bind up it is working.
MT

Do a burnout on a stone driveway or road.

The easiest way is to put your front tires on a tall curb, put it in 4wd and see if the truck struggles to get up the curb. Do a comparison against 2wd to see if there's a difference