Here is my six-wheeled amphibious tank-design with some improvements for the rig.
I tried to create a simple rig animation control with ground detection for the wheels and the suspension.
Also I added some animation-constraints for the steering wheels in the front and the rear, the guns and the outboards.
The animation happens on bone-layer 1.
Just for fun I created a driving through a wall physics animation by using cell fracture.
Feel free to use it for non-commercial projects.