four wheel locked 97 expedition

yesterday i was backing up my lawn to unload some funiture off my trailer i was towing and i put it four wheel well turns out i was in four low and know when i try to unlock it by turning the knob its still in for low no matter what setting im in.tryed nutural and pressing the brake just wont come unlocked can hear it when i turn the switch but nothing and when i hold the brake down it jumps through the three settings but not the for low that its actually in any help

I had the same problem with my 97 Ford F150 with a 5.4L. I don't no if you have the same set up, but my problem was the transfer case motor. The new motor was about $140-$180. It is about a half hours worth of work if that to replace it yourself. Very easy job!