1998 Ford Explorer Sport 2WD w/ 4.0 L OHV. Starts , runs great, except for first thing in the morning. Shifts into reverse fine, but after I back out of drive way and shift into DRIVE, there is a 3-5 second delay and it rolls back then bang it engages. After this first thing in the morning event, it is fine. Changed fluid a short time ago and it is right up to par on the stick. Any ideas???