Automatic Transmission Control Module problems of the 2006 Ford F-250

I was coming back home from vaction in las vagas around just pass state line,when my Ford F-250 hd 2006 went into 4x4 low all by it self. My speed was around 75 miles per hour when the truck went into 4x4 low by it self. If thier whould have been a cars behind me this would been a major crash. My speed went from 75 mph to 20 mph in about 10 -20 seconds,I heard something loud from my transmission and or engine. My truck is at the dealership,I got a call about my truck from the dealership the said the transfer case was bad on the 4x4 control and they were going to look at the transmission.