I added another motor. It might be overkill and it is easy to take it away. I can also easily change the reduction between motors and gearbox. Now it is 1:4. I tried it with the battery with a much steadier output than the transformer. That is good news!
I bought some micro servos to control the transmission. There is not a lot of space, so one of them sits outside the cab.
Here is the motor unit and the transmission:
Here are both units installed in the truck:
This is the truck with only the transmission:
The servos:
Kerst