4x4 "slipping Out"

[renegadeking]

hey guys, i own a 2002 1500 sierra 5.3. My 4x4 is "slipping" in and out of 4x4. When i put it in 4hi or 4low i can hear everything click in. when i turn tight corners the truck "hops" as every truck does in 4x4 when turning sharp. But if i go in the mud its only two wheel drive. if i drive out and turn a sharp corner it hops again, all while the 4hi is engaged and the light is on. i switched the front shift motor on the diff/axle and it is getting power, the drive shaft doesn't spin in 2wd but spins in 4wd. there is no clunking or grinding in the front diff or transfer case. so i have no idea what is the problem, and the local dealer will only help if i bring it in and there are not cheap. Thanks for any help in advance.

[Carder09]

Seems like a familiar post. My old truck did the same thing went mudding and got stuck in such a small rut I thought damn truck was broke but yeah light said it was engaged and runin fine then hit the rut still said engaged finally got it unstuck put it in 2 and left on home, turns out the actuator was bad, went to junk yard and replaced and it was good, also I don't think 4 wheels ever turn without a lockin rear diff. Or a posi rear.