It is windy and the road conditions are bad.

Test the vehicle, going in both directions, on a flat road.

The wheel alignment settings are incorrect.

Adjust to specifications. Refer to Wheel Alignment Specifications in Wheel Alignment.

The steering gear valve is unbalanced (if this is the cause, steering effort will be very light in the direction of lead and heavy in the opposite direction).

Replace the gear valve. Refer to Steering Gear Check Valve Replacement - Off Vehicle in Power Steering System.

The steering shaft is rubbing the inside diameter of the shaft tube.

1. Align the steering column.
2. Replace the steering column as needed.

Refer to Steering Column Replacement in Steering Wheel and Column.

The tire inflation pressure is low.

Inflate the tires to the recommended pressure. Refer to Tire Inflation Description in Tires and Wheels.

The front spring is broken or sagging.

Replace the spring. Refer to Leaf Springs Replacement

The front wheel alignment setting (camber) is incorrect.

1. Check the camber setting.
2. Align the suspension as needed.

Refer to Wheel Alignment Specifications in Wheel Alignment.