I have a problem with my 2004 chevy avalanche. When I push the 4high the transfer case locks in and everything but my actuator on the front axle won't extend out same thing in 4 low it will shift to low gear just no 4 wheel drive. The light on the two wheel drive button stays lit up but whatever other button u push just flashes while the 2 wheel drive light stays on solid. I took the actuator off and put it on my dads truck and it works fine on his. I got under the truck and in two wheel drive u can turn the front drive shaft like normal and when u shift to 4wd it locks in like its supposed to so u can't turn it by hand. Transfer case is doing everything normal but just have a problem somewhere that won't let that actuator extend out to lock in the front axle. Has anyone else had this problem and can someone tell me what I need to fix it. Does the same thing in auto 4wd and the message center just says SERVICE 4WD. Thanks for any info anyone can provide.