Steering Box Hard Spots Explained
A “hard spot” is different from general stiffness or play in the steering. It is a localized wear component within the steering box that can cause the steering to suddenly tighten up within a portion of a turn but otherwise be fine.
What A Hard Spot Actually Feels Like
Hard spots are best described by way of example. Imagine driving along and everything feels to be in order until you hit a spot half way through a turn where the steering becomes very tight for a very short period of time. Upon continued rotation through the turn the steering then returns to normal and continues to behave in the standard manner expected until the same ‘spot’ is once again reached at which point it will once again tighten up for that brief period of time before returning to normal.
Where They Usually Show Up
Hard spots are generally found at centre (dead-ahead) and near full lock in both directions. It is at these positions where the greatest load is placed on the worm gear and ball nut (inside the steering box) whilst it is trying to perform the necessary work to turn the sector shaft to steer the vehicle. Wear or damage to part of the worm track will generally manifest itself when the greatest load is placed upon it.
What Causes Them
Most hard spots can be attributed to one of three items; the ball bearings may have small pits or even flat spots in the surface, which the balls will be forced to run in, causing uneven resistance throughout the lock; the worm track may have worn unevenly causing the sector shaft to bind at certain angles; or the lubricant in the box may have deteriorated to the point that it is no longer providing any cushioning between the moving parts. As stated previously, steering system engineering explains in great detail how worm-and-ball type steering mechanisms are engineered to run smoothly and with minimal resistance throughout the full travel of the steering mechanism. This is made possible by the use of a continuous, smooth path of bearings. Any deviation from this smooth path will result in uneven resistance felt while grasping the steering wheel.
How To Check For One Safely
Support the front of the vehicle on axle stands or a lift. Make sure the engine is switched off. Now slowly rotate the steering wheel through lock to lock. Note the exact spot where the hard spot occurs. Repeat in both directions to see if the same spot occurs every time.
How This Differs From Being Too Tight
The pattern of wear described above will produce a different kind of steering behaviour than a steering box that is set too tight. A steering box that is set too tight will generally feel stiff all the way round. A hard spot on the other hand will generally feel fine almost all the way round and then suddenly get tighter in one place. A test of the steering of a normally worn box would show a smooth and even amount of resistance to turning throughout the lock, whereas a test of a worn box would reveal a hard spot or spots.
Why Ignoring It Causes More Damage
A hard spot does not wear at a constant size. As you use your car and the worn area goes through its load bearing position, it can wear even more, sometimes quite rapidly. The new wear is usually in the form of further grinding of the worn area against the existing damage. What was once a small tight spot can quickly progress to a point where the steering begins to bind or even jumps as you turn through it. This can be very worrying to drive, particularly when cornering.
What You Can Do About It
As a first step to repairing a hard spot, all wear has to be assessed and given a ranking. Provided that there are no signs of severe pitting, bearings with slight wear can be re-drilled for example. If the lubricant in the steering box has dried out and worn components are only slightly affected by this, a complete strip and refit of the worn parts with new lubricant can be a cost effective repair. However, if there are signs of severe pitting and flat spots on the bearings or worm track, a complete re-condition of the steering box (rebuilding) is required.
Why It’s Worth Sorting Properly
These items are made to specific engineering tolerances. So a ‘hard spot’ left to worsen will eventually fall outside of the acceptable levels to be considered safe to be on the road. And the general guidelines on road safety and vehicle maintenance generally relate to aspects of a vehicle and its maintenance in relation to potential accident situations. Steering is one of the main aspects and could potentially cause an accident should its components not be properly maintained.
Catching a hard spot early enough means you can get it fixed with a local repair that will cost less than a full Steering Box rebuild. A Steering Box that is worn to this extent can need a complete rebuild.
