There are two basic categories of steering systems, those with pitman arms and a steering box, usually called recirculating ball, and rack and pinion steering. Pitman arm systems are used on vehicles intended for all-out off-road driving, such as Jeeps, and heavy-duty trucks. Newer cars and unibody trucks use rack-and-pinion.
PITMAN ARM
Pitman arm steering systems give a larger mechanical advantage and thus work well on heavier vehicles. The steering wheel connects to a shaft leading to a steering box. On the other side of the steering gearbox, a lever arm comes out, the pitman arm, which connects to the links leading to each wheel. The traditional reward of these systems is that they offer more mechanical advantage. Power steering has made this less important. This design is still used for a lower price, lighter weight, and resistance to damage. Off-roaders prefer not to be towed home when they bang into an obstacle or power through a rut.
In a recirculating ball steering box, there is a worm drive with many more turns giving it a fine pitch and precise control. The worm drive is surrounded by ball bearings, making a sturdy mechanism less likely to be damaged in demanding use. The worm drive turns when the steering wheel is turned and forces the ball bearings to press against the channel inside the nut. This causes the nut to move along the worm drive. The nut has a couple of gear teeth cast into the outside of it, and these mesh with the teeth on a sector gear attached to the cross shaft.
RACK AND PINION
Modern passenger vehicles have this type of steering due to its simplicity in construction and low cost. Rack and pinion systems give a much better feel for the driver, and there isn’t the looseness of pitman arm systems. However, unlike pitman arm systems, they have no adjustability, so wear requires replacement. In a street-driven car, this much wear is unusual, but rock crawlers would be replacing their steering systems regularly if their vehicles used rack & pinion systems.
The steering rack in a rack and pinion system is a long, toothed bar. On the end of the steering shaft from the steering wheel, there is a pinion gear meshed with the rack. The pinion gear turns when the steering wheel turns and moves the rack left or right. The front wheels turn for steering because the rack is attached to suspension components at each wheel. The manufacturer can change the steering ratio by altering the number of teeth on the pinion gear. The recirculating ball steering system has more parts; rack and pinion steering have fewer parts and fewer complications. With fewer parts, you get superior driving involvement. Fewer parts give you less friction, making the steering feel more reactive and controllable. As an additional positive, a rack and pinion steering system is lighter than a recirculating ball system, providing better fuel mileage.
Repair
We at Fremont Foreign Auto Repair have considerable experience with both steering systems. We have hard-core off-roaders among our technicians, as well as performance-car drivers. There are numerous joints in a steering system; they will wear out over time and use. If your car’s steering wheel shakes when you drive, there may be looseness in your steering system. If your vehicle has an adjustable steering wheel, a joint in the upper steering column may be worn out. Lower down in the steering column, there is a flexible joint that frequently needs replacement in a high-mileage car. If you frequent heavily-pot-holed roads, and who doesn’t in California, your pinion gear, rack, or both may be worn out.
At Fremont Foreign Auto, we have dedicated auto repair experts who can diagnose your shaky steering wheel and replace only worn parts. We don’t replace parts one after another, hoping to find the one causing the problem. Call us at 510-793-6067 or visit our website to get a quote and book an appointment for a steering gear inspection or any service you require.
