The tire air pressure is too high.

Deflate the tire to the correct pressure. Refer to Tire Inflation Description in Tires and Wheels.

The wheel bearing are improperly adjusted.

Adjust the wheel bearings to specifications. Refer to Wheel Bearing Adjustment in Front Suspension.

The camber adjustment is incorrect (Negative camber contributes to road shock).

Adjust camber. Refer to Wheel Bearing Adjustment in Wheel Alignment.

The spring is broken or sagging.

Replace the spring. Refer to Leaf Springs Replacement in Front Suspension.

Inspect for defective shock absorbers.

Replace the shock absorbers. Refer to Shock Absorber Replacement in Front Suspension or refer to Shock Absorber Replacement in Rear Suspension.

The suspension components are loose.

Inspect, repair, adjust, the components as needed. Refer to King Pin Bearing Preload in Front Suspension.