What could make your transmission think the vehicle is in 4x4 low when it really in 2 wheel drive?

My 1997 Ford f150 is stuck in 4x4 low but only the transmission is in the low gear setting what could be causing this?|||put the 4x4 switch in 4x4, drive strait for 15 feet. then put the shifter in neutral,then back up 15 feet. then change the switch to 2 wd, and drive forward. the transfer case can get in a bind and not switch from 4x4 to 4x2 mode if the drive-train has a bind on it.|||maybe you have an electrical circuit that is out of whack. get it looked at.