I over-engineered independent suspension for the Monster Truck [60402]

Front view

Rear view

Without wheels

Suspension mechanisms isolated. The upper brown axles are the main attachment point to the body while the lower ones slot into runners under the chassis

Close-up

Side view showing the runners which contain the suspension movement

Close-up of the runner

Two rubber bands go on each wheel from both sets of blue bushes. I've built the mechanism in person and it has a nice soft but springy bounce with a hard stop just before the wheels hit the wings (fenders). There's very little forward/backward travel on the wheels. You can find the studio file here: mediafire.com/file/16mhcf42jgjr3z6