The first step I made was the drive. On the picture, you can see the axes and the gears.
The second picture shows a differential.
On the 3rd picture, you can see the two differentials with the gears. They're directly connected to the wheels.
The next picture shows the 3:1 gears. The motor is connected to the small gear and the wheels are connected to the larger wheel.
The last picture shows the motors. They made the project much bigger.
The second part I made was the gear. It was very hard to connect the front to the rest of the moddel. You can see the technic of the gear at the first image.
The second one shows the ultrasonic sensor in the front of the gear.
The third shows the toothed bar. The last picture shows the gear translation I used to change the direction of the axes. The black gears are well for the propose.