Steering Boxes

There are two types of vehicle steering systems, the rack & pinion, which is commonly used on modern cars, trucks, and SUVs, and the conventional worm gear recirculating ball steering box, which is still employed on some trucks and SUVs but is mostly found on older vehicles. Both designs convert the rotational motion of the steering wheel into turning motion at the front wheels. The conventional steering box accomplishes this with a worm gear, ball nut, and sector gear and shaft housed in the steering box, and steering linkage consisting of a pitman arm, idler arm, center link, and tie-rods, which are attached to the steering knuckles/spindles where the wheels are mounted.

The steering column shaft is attached to the worm gear. When the steering wheel, and in turn the worm gear, is turned, it acts on the ball nut causing it to move up or down the worm gear depending on which way the wheel is turned. The worm gear and ball nut are not threaded, and they do not directly contact one another. Rather, both parts have machined grooves on which a series of ball bearings ride. The ball bearings reduce friction and ensure smooth operation without play, which would cause loose steering. Ball guides recirculate the balls through the gear and nut, ensuring even wear and giving this steering system its name. Gear teeth cut into the outside of the ball nut engage with teeth on the sector gear and shaft. The pitman arm connects the sector shaft to the center link, which is supported at the other end by the idler arm. The tie rods are attached to each end of the center link. When the steering wheel is turned, the pitman arm forces the center link and tie-rods to move laterally, thereby turning the front tires.

Manual steering boxes were common on many vehicles in the past, but just about all newer vehicles with this system have hydraulic power assist. An engine driven pump supplies pressurized fluid to the steering box via a flexible high-pressure hose, and fluid is returned to the power steering pump reservoir through the low-pressure return hose. Inside the steering box is a valve and torsion bar assembly that controls fluid pressure on each side of the ball nut. When the vehicle is driven straight ahead and the steering wheel is centered, there is equal pressure on both sides of the ball nut. When the steering wheel is turned, the torsion bar inside the valve twists and directs fluid pressure to one side of the ball nut while releasing fluid pressure from the other side to the reservoir, creating power assist. When the steering wheel is released, pressure is again equalized on both sides of the ball nut.

Leaks and loose steering are the most common conventional steering box problems. Leaks are most common at the worm gear shaft and sector shaft seals, and at the sector shaft cover. If the steering wheel can be turned back and forth quite a bit without the front wheels moving, a worn steering box may be indicated. However, the steering column and steering linkage should be checked for wear and play before the steering box is condemned. Check for play in the steering column shaft bearings, mounts, and couplings, and check the idler bushings and all steering linkage ball studs. If all other components check out OK, and the excessive looseness is isolated to the steering box, first try adjusting the worm gear bearing preload and the sector shaft lash according to the manufacturer’s instructions and specifications. If these adjustments don’t solve the problem, the gearbox should be replaced.

No matter what your repair or upgrade needs are or what you’re working on, we have the steering box assemblies and related components to restore safe, predictable, and easy steering system operation. We offer manual and hydraulic power assisted steering box assemblies that are manufactured to original equipment specifications. We also have seals, gaskets, bearings, valves, sector shafts, and repair and rebuild kits if you want to tackle repairing or overhauling the steering box assembly yourself. In addition, we offer steering box brackets and mounts for select vehicles.