Just changing my saphire 4x4 gear box and trying to fit the rear prop shaft onto the black rubber 50p situatedon the outward end of mt75. It will only fit one way. ie the rods will pass through one set of 3 holes and not the other. The others seem just slightly out . the three rods attached to the end of the gear box will also only fit through the same three holes leave the other three useless in both cases. am i missing a trick?