I place the gearbox front of the engine. Switching system is moved underneath the gearbox and gearbox levers are in center of car. I can put in place the axle of HOG in frame center, no need to by-pass the gearbox. Traditionally, I must use 3 16t double bevel to by-pass the gearbox because it has a 7-Stud width. With this system, axle of HOG is placed in the center of car. The construction is centered in the frame. To switch the gearbox, the two gearbox levers are placed side by side of the axle HOG. For the principal gearbox Control lever, It is created with this part : 6572 - Technic Suspension Steering Link. It's enable to build a 2-axle Joystick. At least, the drive train axle is placed on the left side of the gearbox and by-pass the gearbox control lever with 1-stud offset. Basically, this construction permit me to have a centered construction for the axle HOG (with no 16t), drive train, and gearbox lever. Special thanks : To Erik Leppen, who invented the system of gearbox lever axle. Video : http://www.youtube.com/watch?v=_AEQLupJxR8