LST 2-speed problem

I've got a strange problem with my LST. It has got a 2-speed. But the problem is that it can only run backwards. If I turn the large spur (1st gear) one way, the car does move backwards, if I move the spur to the other way it doesn't move at all? And if I turn the small spur (2nd gear) it does nothing to, doesn't matter if I turn it to the right or left. (But that is right, isn't it?)

Does anybody know what I did wrong? (I completely disassembled the LST, and re-assembled it)

Thanks,

Patrick