Jimmy stuck in 4x4 won't change

I put my jimmy in 4 wheel drive during a cold snap (minus 23 deg. celcius) I then days later pressed the 2wd button and it just clicks, it won't go into 2wd or 4 low. The 2wd light flashes and then switches back to 4x4 light. With the engine off but key on, I can hear something like a electric motor whining or buzz from the transfer case. Sounds like its try to do something. Any suggestions. Please...

I found with my 96 that I have to let it run a while to get it to switch back. Once it warms up it switches right back.