I had something weird happen with my Expedition this weekend after driving in a snowstorm. I shut off the 4WD and while driving in regular drive the speddometer indicated I was going 40 or 50 while I was only doing maybe 15mph. I was only going around the block and after a few hundred feet, a knock sound came from under the chassis like near the trans and everything went back to normal. But I haven’t used 4WD since then because I’m nervous something is really screwed up. Any thoughts on what this might be?
A rear brake could have been frozen, or even a front brake. Old 4WDs had problems with ice on the front driveshaft U-joint. Water would drip from the cowl and freese immediately. The most common effect was being stuck with front hubs locked. It did not happen very often. Once the hubs were unlocked, you could move again. It sounds like you broke the ice.
That sounds great…I had visions of this being a huge repair…thanks for the info!