I own a 97 Explorer Sport equiped with Control Trac 4X4, it's go 70,000 miles. About a year ago I was in a pretty serious accident. In addition to the extensive body damage the entire frame had to be replaced. All undamaged origional parts were transfered to the new frame and the body was bolted back on. About four months later When I started it and backed out of a parking space the ffront diff. locked in 4X4 even though the selector switch on the dash was in auto. Once I drove out of the parking lot it dropeed back to normal and the 4X4 lights on the dash blinked. It didn't do it again for a few months. Jusst recently It started again and I brought it to Ford, they couldn't find a problem and the computer logged no codes. I was told that unless I could bring it to tthem (Ford) when it was locked up they couldn't help me. It does it on a semi-regular basis but as soon as I get above 35 mph it drops back to 2WD. I had a complete transmission/transfer case service done a week ago and everything was fine. I was able to get it to lock up for the transmission guys. Even with their computer connected at the time they got no codes. We also checked the ABS system to see if one of those sensors may be causing a problem, no luck. I'm sure that this is an elctrical problem that we can't find, I suspect a bad actuator. The 4X4 systems still works fine and the trans. works perfect. I'm running out of ideas quick and would like some help. Anyone got a magical trick?