I have a 2005 Chrysler town and country van. Never had a problem with anything under hood. Last weekend my husband was going up a hill that was a little muddy and go it stuck. After getting it unstuck the reverse wouldn't work. It goes in drive and will drive forward without hesitation. When shifted into reverse it acts like it is in neutral and revs the engine but doesn't move at all. I want to change the transmission filter and replace oil. I don't think it's the transmission its self but I'm not a mechanic so I don't know, but I'm willing to try anything before replacing a transmission. Any suggestions?