Here is my six-wheeled amphibious tank design.
All components are individual objects and are saved separately in the fbx folder, so you can easily setup and equip the tank in your game project, I have tested it in Unity and UDK.
Textures: Normal maps for GLSL and DirectX, color, metalness, roughness, ambient occlusion and curvature maps.
Maximum texture resolution for the different components: Wheels(4K), gun(4K), exhaust pipe(4K), outboard(4K), antenas(4K), door(4K), containers (4K), Machine gun towers(4K), tank chassis(8k).
Modelling and texturing in 3d-Coat, for rigging and animation I used Blender.
Test in UDK: https://www.youtube.com/watch?v=znk77snr3E8
Test in Unity: https://www.youtube.com/watch?v=hM_QVJJX8oo&feature=youtu.be
Test in Blender: https://www.youtube.com/watch?v=c83JOb0YIPI