Scott B

First, I am new to the forum! I want to thank anyone and everyone who can help me. I have a 2007 New body style Chevy Silverado. I switched in to 4wd-hi to get out of some mud. But now I cannot get out of 4wd. I can switch between 4wd-hi and low with no problem but it will not switch out of 4wd to 2wd. When I switch the **** I can here a sound, which I believe is the actuator (maybe?) but it does not switch out of 4wd. When switching from 4wd hi to low or visa versa I hear the same sound (actuator sound I believe) but then seconds latere I can hear and feel it switching from hi to low and low to hi. My first thought was to check fuses, however I can't find any fuses that state 4wd on the inside or outside box. I bought my truck used and it did not come with a manual. Plus I would think if it was a fuse then it wouldn't be working bwteen 4wd-hi and low either. So, I'm really not sure what to do at this point. Any help would be greatly appreciated.