Steering Box Problems

In most cases, a steering box needs rebuilding because it has become so loose that it is hard to keep the car going straight down the road without a lot of constant correction. Causes of this looseness is due to excessive play in the bearings or gear wear surfaces or play in the bearing and gear mesh adjustments. This looseness is caused by two main problems; wear and corrosion. Wear is caused by high mileage, poor lubrication and improper adjustment. Corrosion is caused by water getting inside the box and pitting the critical surfaces.

The three most important parts in the steering box are the Input Shaft/Worm Gear, the Rack Block and the Sector Shaft. It is the condition of these three pieces that determine if a rebuild is possible. Each one has its own vunerable areas that must be examined to determine if the part is re-useable.

The Input Shaft is turned by the steering wheel. Before 1968 (except in big Fords and trucks) the Input Shaft was a long piece that went all the way up to the steering wheel. Starting in 1968, Ford went to a short Input Shaft design with a coupler connecting the another shaft that went to the steering wheel. This was due to the implementation of the collapsable-style steering column. Regardless of the Input Shaft length, the end that went inside the steering box was made as a Worm Gear. The recirculating balls ride in this twisted gear, moving the Rack Block up and down its length.
There are two areas on the Input Shaft that must be examined.

The grooved surface of the worm area on this Input Shaft is pitted due to abrasion by metal particles. This type of damage is usually found in the center of the worm area, the place where 99% of all driving is done. Most likely the hard-chrome plating has flaked off of some of the balls or one or more of the balls has broken apart and fragmented inside the Worm Gear/Rack Block area. This hard metal has been ground into the Worm Gear, pitting it as you see here. This Input Shaft cannot be used. The recirculating balls will be ground up by the rough surface and the problem will quickly escalate. This Input Shaft will have to be replaced.

The grooved surface of the worm area of this Input Shaft is pitted due to corrosion. Water has gotten inside the box, settled around the recirculating balls, and rusted the gear. As in the example above, this Input Shaft cannot be re-used. The rough surface will only destroy the recirculating balls and damage it further until it locks up.

This picture shows the end of the Input Shaft where the lower Input Shaft Bearing rides. There is a similar area at the other end of the Worm Gear. The surface has been pitted from corrosion. This is very common since this is the lower-most area inside the box and where water will eventually settle. Obviously, a bearing will not ride smoothly on this surface and a proper bearing-load adjustment cannot be made.

The grooved surface of this worm gear has a faceted look to it. There are small flat areas on the sides of the groove, right where the recirculating balls roll. This irregular wear pattern is usually found in the center of the worm gear. A small amount of this pattern is usually not harmful but will cause accelerated wear. A steering box used in a car that is not driven much will probably be alright. If the car will be driven daily, or have a lot of miles put on it, a shaft with this type of damage should be replaced.

The Rack Block does double-duty. The inside is grooved to match the Worm Gear. The recirculating balls roll between the Worm Gear and the Rack Block. The outside of the Rack Block also has four teeth on it to mate with the teeth on the Sector Shaft. As the Rack Block moves up and down the Worm Gear, these outer teeth cause the Sector Shaft to twist, which moves the steering linkage and turns the car. The condition of the inside grooves and outside teeth of the Rack Block are critical.

The grooves inside this Rack Block on the left are rough but not pitted. This was caused by the recirculating balls having their hard chrome plating worn gradually worn away and causing this wear on the grooves. Sometimes this damage can be partially removed and the block re-used. If a fair amount of the grooving is damaged in this way, it is best to replace the Rack Block.

The grooves inside this Rack Block on the right are pitted due to metal contamination. Some of the recirculating balls may have shed their hard chrome plating or possibly broken up inside the rack. The action of the balls rolling on the Worm Shaft has ground the pieces into the grooves and damaged them. This Rack Block is not re-useable. Any further use will cause the remaining balls to break up and damage the surface even more. A Rack Block damaged like this must be replaced.

One of the most critical points about rebuilding a steering box, and the one most often misunderstood or ignored by rebuilders, is the Gear Mesh Load in the center of steering box travel. Because a steering box spends 99% of its time driving in a straight-ahead condition, the engineers designed in a "tight spot" in the center. This causes the box to have the least possible play while going straight down the road. Without this center tightness, the car would want to wander on the road and would not hold a line well, twitching off whenever the tires encountered something on the road surface. This is the reason most steering boxes are rebuilt - to minimize this looseness. This tight spot is built into the center two teeth of the Rack Block and the space between them. As the teeth on the Sector Shaft move through this section of the Rack Block, the clearances between them gets measurably tighter in the very center. A Rack Block that is damaged or too worn in this center area to provide a tight spot with the Sector Shaft, is too damaged to be re-used and must be replaced.

Look at the faces of the teeth. The fine lines you see etched into the surface of the teeth are the original factory tooling marks from when the part was machined. These are particularly evident on the faces of the outer teeth since they receive less wear. The more of these tooling marks that are present, the less wear there is on the teeth and the better they are. The most important thing is the wear on the inside faces of the two center teeth. The Rack on the left shows only a slight polishing on its face and most of the tooling marks still evident. You can feel the smoothness of the marking with your fingernail but do not feel and gouging or pitting. The Rack on the right has an obvious shallow area worn into the tooth face that you can easily feel.

The Rack Block on the left is as good as new, despite having many miles on it, and can be re-used. The Rack Block on the right will have too much clearance in the center and will not produce a tight spot when meshed with the Sector Shaft. It cannot be re-used and must be replaced.
If the center teeth of the Rack Block are worn enough that you can easily feel a groove or low spot in its surface, it cannot be re-used. A Rack Block with any of the inner tooth surfaces gouged or pitted from corrosion, cannot be re-used.