I am planning on leaving on a 500 mile trip Monday... . today my truck would not shift into overdrive... is it ok to travel this way and what should I look for as a fix? If I wait to go to the not so trusted dealer I will not be able to make it to my destination as planned. Thanks in advance for your help. 2003 4X4 extend cab 40 K miles # 47 trans... automatic ... yes it's a diesel.