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. Just for fun I created a driving through a wall physics animation by using cell fracture.
Here are some download links:
Sketchfab https://sketchfab.com/3d-models/amphibious-tank-new-rig-e12570cdfc1a4caaade442f82c4ca7fb#download
Blendswap https://www.blendswap.com/blends/view/93599
Cgtrader https://www.cgtrader.com/free-3d-models/vehicle/military/amphibious-tank-new-rig