4 wheel drive
 

while trying to pull a small stump out of my yard, I noticed that only my back wheels were spinning (wifes observation). I checked to see if my hubs were locked and had my wife back up a bit and pull forward and saw both drive shafts spinning, but once I hooked but up to the chain and had my wife step on the gas the front drive shaft wasn't spinning and saw only the back wheels digging in.Any ideas what would cause this. Thanks. Oops I have a 1990 k5 5.7 liter, 700R4 and new rebuilt NP 241. Posi rear end and Spool up in the front diff.

the manual locks are probably just all gummed up with dirt or grease. one way you can kinda check is put the truck in 2wd and lock the hubs then just reach behind the knuckle and try to spin the ujoint thats back there. if one spins freely then that one is not engaging.

probably just take off the outer lock out on the end of the tire and clean it up. dont grease it up that makes it bind, maybe a really thin layer but dont glob it up in there