My 9398 crawler going in reverse way I built 9398 crawler set and everything seemed OK. 

However, when I moved the RC tumbler up, the crawler went back, and when I moved it down, the crawler went forward.

On the battery box I saw tumbler and changed its position, but nothing changed.
I also changed the order of connection motors to box, which also didn't help. 

P.S. Turns work fine.
From the power functions FAQ:


  
  Why does my Power Functions model drive backward when I want it to run forward? You can change the direction your model runs by flipping
  the small black switches located on each side of the channel selector
  of your IR Remote Control.