I've got a stock 1984 M1008 that I use solely for snow plowing. I plow with the transfer case in low 4wd. On a few occasions I have spun all four tires at the same time when pushing a heavy load on packed snow. I use V-bar chains on all four wheels. Is there some locking or limited slip feature on the front differential (I wouldn't think so), or is it because the chains prevent individual wheel spin? I'm certain of the four wheels spinning by observing the four tire grooves left in the packed snow surface.