Yes they can be too close.... Will bind... too loose will strip.... Place a piece of folded notebook paper between the gears and the clutch bell(spur gears) tighten down until paper is snug between gears... remove the paper, now you have the correct mesh... If paper comes out all chewed up.. you have it too tight.... Once you do this enough you will see how the mesh is set... I do mine by eye and feel... Don't do this until you are very experienced or you will destroy gears all day.... also, please check and make sure the chassis is not bent in the rear..... are the gears meshing straight ? sometimes that can be a problem especially after a hard crash on the tail of the truck.......