I don't know if it will help, but here is a way to make wheels following the ground:

• Create a cube (the vehicle), a wheel, and a small plane.
• Parent the wheel and the plane to the cube.
• Put the plane under your wheel, subdivide it a bit, assign a vertex group to the whole mesh.
• Give it a Shrinkwrap modifier, choose the ground as the Target
• Give your wheel a Copy Location modifier, choose the plane as Target, select the plane's vertex group in Vertex Group, deactivate the X and Y axis so that it only moves on the Z axis, activate Offset and place the wheel at its right position, on the ground and above the small plane.
• Move the cube to test the animation, the wheel should follow the ground.
• Copy paste x 4 the wheel + its plane.

I don't know if it will help, but here is a way to make wheels following the ground:

• Create a cube (the vehicle), a wheel, and a small plane.
• Parent the wheel and the plane to the cube.
• Put the plane under your wheel, subdivide it a bit, assign a vertex group to the whole mesh.
• Give it a Shrinkwrap modifier, choose the ground as the Target
• Give your wheel a Copy Location constraint, choose the plane as Target, select the plane's vertex group in Vertex Group, deactivate the X and Y axis so that it only moves on the Z axis, activate Offset and place the wheel at its right position, on the ground and above the small plane.
• Move the cube to test the animation, the wheel should follow the ground.
• Copy paste x 4 the wheel + its plane.

I don't know if it will help, but here is a way to make wheels follow the ground:

• Create a cube (the vehicle), a wheel, and a small plane.
• Parent the wheel and the plane to the cube.
• Put the plane under your wheel, subdivide it a bit, assign a vertex group to the whole mesh.
• Give it a Shrinkwrap modifier, choose the ground as the Target
• Give your wheel a Copy Location modifier, choose the plane as Target, select the plane's vertex group in Vertex Group, deactivate the X and Y axis so that it only moves on the Z axis, activate Offset and place the wheel at its right position, on the ground and above the small plane.
• Move the cube to test the animation, the wheel should follow the ground.
• Copy paste x 4 the wheel + its plane.

I don't know if it will help, but here is a way to make wheels following the ground:

• Create a cube (the vehicle), a wheel, and a small plane.
• Parent the wheel and the plane to the cube.
• Put the plane under your wheel, subdivide it a bit, assign a vertex group to the whole mesh.
• Give it a Shrinkwrap modifier, choose the ground as the Target
• Give your wheel a Copy Location modifier, choose the plane as Target, select the plane's vertex group in Vertex Group, deactivate the X and Y axis so that it only moves on the Z axis, activate Offset and place the wheel at its right position, on the ground and above the small plane.
• Move the cube to test the animation, the wheel should follow the ground.
• Copy paste x 4 the wheel + its plane.