The road or wind conditions are poor.

Test drive the vehicle going in both direction on a flat road.

The front wheels are misaligned.

Inspect the alignment of the front wheels and correct, if necessary. Refer to Wheel Alignment Measurement in Wheel Alignment.

The steering gear valve is unbalanced.

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

Replace the steering gear. Refer to Steering Gear Replacement .

The steering shaft is rubbing the inside diameter (ID) of the shaft tube.

Align the steering column. Refer to Steering Column Replacement in Steering Wheel and Column - Standard or Steering Column Replacement in Steering Wheel and Column - Tilt.

The tires are worn or bad.

Replace the tires. Refer to Tire Mounting and Dismounting in Tires and Wheels.

The tire pressure is low.

Adjust the tire pressure. Refer to Tire Inflation Pressure Specifications in Maintenance and Lubrication.