My wife's 2004 Grand Cherokee Laredo, 4.0 6 cyl, Auto Trans, Selec-Trac part-time 4wd system, just started having a problem where it won't switch back into 2wd. The shifter goes into the 2wd position, but it remains in 4wd. I have tried the reversing the auto shifter and backing up a few feet, after shifting it into 2wd trick, but it still doesn't work. It sometimes takes days to unshift. Is there an easy fix I can do myself? I have an appointment for the Jeep dealer at the end of the week, since it should be covered under waranty, but I hate dropping it off for days when the wife uses it to take kiddies to school, if it is an easy fix, that I could do, that would be best. Any comments are appreciated.