There is a lot of buzz about steering box versus rack and pinion. You can search for kits that convert a rack & pinion car to a steering box and you won’t find such a kit. Unbelievable as it sounds companies are introducing “new” steering box replacements like the Delphi 600-series power steering box. This is the equivalent to introducing “new” flint lock rifles and claiming they are some how better than a cartridge fed rifle, it just is not true. If you like old stuff there is nothing wrong with a flint lock, or for that matter a steering box, but beware of an argument that old is better. Let’s examine the dear old steering box and see what the facts are.
Steering Feel
This is a subjective area of discussion in talking about handling, but a very important topic. Modern vehicles have significantly better “feel” than those manufactured in the ‘60’s through the ‘80’s. It is not about wear either, it’s about design. If you just look at the number of parts in the linkage between the steering wheel in your hand and the front wheels there is a major difference in opportunity for slop, friction and flex between a modern rack and pinion design and an old steering box design.
On a steering box design the path to the wheels starts with the box itself which has internal gear lash (play). Next the pitman arm with a joint linking it to a center link (track rod) which as two joints for each inner tire rod. In addition to this the center link has a pivot point called an idler arm for stabilizing the end, and finally the tie rod end. Altogether seven separate connections until you are actually turning the wheel, not including the gear lash in the steering box and the clearance for the re-circulating ball bearings inside the box.
Contrast this to a rack and pinion which has gear lash as well, but no re-circulating ball bearings, and has only two joints for the tie rod ends, and two inner tie rod joints. You can see how even in a new setup there are three more points to add play, and friction, and flexing to the feel. This linkage path is integral to another element that is inherent to both designs; on center feel.
On Center Feel
This is the most noticeable difference between steering box steering and rack & pinion steering. It can be best described by the response you receive while cruising with the wheel “on center”. The vehicle moves when you steer without lag or play. Even a new steering box with new steering parts will have lag. That is because of the extra joints for motion in the system as described in the Steering Feel Section. In addition to this it is very difficult to “back drive” a worm and segment gear found in a steering box. Back drive is when the front tires try to drive the steering wheel back to the center position. The incline of the worm gear ( a spiral shaped gear) introduces a lot of friction that must be overcome by the natural tendency of the steering geometry to self center. The result is a vague and drifty with no center feel.
Rack and pinions have a different design with a horizontal “rack” of gear teeth that are meshed with a pinion gear. This is a much easier physical arrangement to back drive since there is no steep incline to drive against. It is also directly driving the steering with the tie rods with no additional linkage to flex. These facts plus only four steering joints to add friction make the steering try to center itself. This gives the driver a solid, crisp on center feel that is ready to accept steering wheel inputs.
Corvette Owners With Factory Power Steering: In addition to these facts your Vette has a power steering servo valve at the end of the pitman arm. This is not like most steering box equipped cars which have the power boost built into the box. On the Corvette the pitman arm has a joint that moves as you turn the wheel. The force of turning the wheel causes a force sensor to activate the hydraulic ram in the direction you steer, and applies power boost to the to the steering. Every control system has “dead band”, an area where no control boost is applied. Some dead band is necessary, but this dead band outside the box when added to the natural poor back drive of a steering box makes the on center position vague with a lot of steering wheel “sawing” to keep the car pointed straight. This only gets worse with age as the joints wear.
Steering Feedback
All of the previous discussion about feel and on center feel is the basis to understand steering feedback. From the basic design limitations of a steering box it is easy to explain why a car with this system has very imprecise feedback to the driver. All the force necessary for you to feel what the car is doing is absorbed in rotary joints and linkage needed to make the system work. If you add wear on those joints you have a steering system that is ambiguous to drive, it is not “telling” you what you really need to know. This is especially true if you are cornering hard up to the limit of available traction. The last thing you want when the tires are howling is to have no clue what the front end is doing.
Feedback is also affected by the amount of boost your power steering has, if so equipped. This is why a few drivers prefer manual steering over power, but that does not need to be the case. A properly designed power steering system is just as good if not better that a manual system. For one thing fatigue is a factor. That is why most race cars have power assisted steering. Make sure you consider the amount of boost you will get if you are converting. There are ways to limit this with certain pumps. It is well worth the effort to have a car that handles well at speed and that you can easily maneuver to park with the added friction of wide tires, so don’t dismiss the power steering option.
Conclusion
If all this doesn’t sway your thinking then stick with the “older is better” crowd but consider this; 99% of new cars & even pickups, and virtually all race cars have rack and pinion steering. When it was introduced to the racing world it was seen as a major technological advancement for precision and control. It is demonstratably more precise and “feels” like no tweaked up steering box can ever feel, new or otherwise. Converting to rack & pinion is the quickest way to update your classic to twenty first century steering that you will notice a significant improvement in drivability. You will not find a kit on the market that converts a rack and pinion car to a steering box. So why wait? Move up to rack & pinion and put the fun & control back in driving!
Why aren’t there steering box conversion kits?
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