If we mention rack and pinion gears, you may not have a clue what we’re talking about. However, if you have a car, the chances are that you use rack and pinion gears every time you drive. Here, we take a closer look at rack and pinion gears, what you need to know about how they work, and how to care for them.
- What Are Rack & Pinion Gears?
- What Does Rack and Pinion Steering Look Like?
- How Does a Rack and Pinion Gearset Work?
- What Is a Steering Ratio?
- What Is Power Rack & Pinion?
- What Are the Signs That My Rack and Pinion Gears Are Failing?
- How Do I Check My Rack and Pinion Gears?
- Potential Rack and Pinion Problems
What Are Rack & Pinion Gears?
Rack and pinion gears convert the rotational motion of your steering wheel into the linear motion that is required to turn your car’s wheels. This is why they are used in the steering systems of most types of car. When you turn your car’s steering wheel, it will rotate a gear. This, in turn, will engage the rack. When the gear turns, it will slide the rack to the left or right depending on the direction in which you turned the steering wheel, allowing you to effectively maneuver your car with less effort than would otherwise be required.
What Does Rack and Pinion Steering Look Like?
Rack and pinion gears are rapidly becoming the steering system of choice if most SUVs, small trucks and cars. It’s a relatively simple mechanism that contains a gearset enclosed within a metal tube. Both ends of the rack protrude from this tube, while a rod known as the tie rod is connected to both ends of the rack.
The steering shaft is connected to the pinion gear. This allows the steering wheel to spin the gear whenever it’s turned, moving the rack. The tie rod on both ends of the rack is connected to the wheel via a steering arm.
How Does a Rack and Pinion Gearset Work?
Rack and pinion gears perform two functions:
- They convert the steering wheel’s rotational motion into linear motion that is then used to turn the car’s wheels.
- They provide a gear reduction that makes turning the wheels easier.
On the average car, you need to turn the steering wheel through three or four complete revolutions to make its wheels turn from far right to far left and vice versa. Without rack and pinion steering, fewer revolutions would be required, but moving the wheel would require far more effort.
What Is a Steering Ratio?
Steering ratio is a term used to describe the ratio of how far the steering wheel is turned compared to how far the car’s wheels turn as a result. So if, for example, a full revolution of the steering wheel causes the car’s wheels to turn 20 degrees, the steering ratio would be 18:1 (or 360 divided by 20).
When there is a high steering ratio, the steering wheel must be turned more in order to make the wheels turn any given distance—but less effort will be necessary due to a high gear ratio.
Usually, sportier, lighter vehicles have a lower steering ratio when compared to trucks or larger cars. A low ratio allows the steering to have a more rapid response – there’s no need to turn your steering wheel so far to make the wheels turn a certain distance. This is an appealing trait when you’re driving a sports car. Smaller cars are sufficiently light so that, even with a low ratio, the effort needed to turn the wheel won’t be excessive.
There are some cars that have variable-ratio steering. This type of steering system features rack and pinion gears that have a different number of teeth per inch (also known as tooth pitch) in its center compared to the number of teeth found on its outside. As a result, the car can respond more rapidly when beginning a turn. It also reduces the effort required when the wheel is close to its turning limits.
What Is Power Rack & Pinion?
As well as standard rack and pinion gearsets, there are also power steering systems that use rack and pinion gears. These have a rack with a different design. A cylinder is contained in part of the rack. In the center of it is a piston, which is linked to the rack. Two fluid ports can be found, one on each side of this piston. When high-pressure fluid is supplied to the piston on one side, the piston is forced to move. This, in turn, causes the rack to move, supplying the power assist.
What Are the Signs That My Rack and Pinion Gears Are Failing?
There are several symptoms to look out for that indicate your rack and pinion gears are failing. These include:
- Discolored or low fluid – you should check your power steering fluid to note its condition and level. If the level is too low, you should add more then take a test drive. On the other hand, if the fluid isn’t the right color, contaminants or water may be in the system, so you should have a power flush carried out. Should the fluid be foamy, air may be getting into your system, possibly via a cracked hose line. Check the hose with the larger diameter (the low-pressure line). If it is damaged, replace it.
- Leaks – If there is any evidence of a brown or red fluid under the car, you may need to check other components as it may not always be the rack that is at fault. Check the level of power steering fluid and add more if the level is low. It can be hard to determine the source of a leak, so it may be best to seek help from your local garage.
- Wandering steering – if your car struggles to drive in a straight line, you should arrange to have an alignment check carried out professionally. If that doesn’t resolve the problem, it could be the rack at fault.
- Burning smell – burning smells may not be due to the rack, but if the smell is coming from your engine bay, there’s a good chance the rack could be over-heating. A fluid flush may solve this, but if not, you should seek professional advice.
- A dead spot – sometimes, a numb spot can appear when your steering wheel is in neutral where no resistance can be felt. This will make the steering wheel feel as if it’s disconnected from the remainder of the vehicle until you’re able to turn it sufficiently for it to engage and steer once more. If this happens, your gears could be worn out. You’ll need to take your car to a garage for a repair and replacement.
- Grinding noises – if you notice a grinding sound when you turn a corner at a low speed, this could be a sign that the rack and pinion gears are damaged or out of alignment. You must get this checked rapidly, or serious problems could occur.
How Do I Check My Rack and Pinion Gears?
If you need to check your vehicle’s rack and pinion gears, you will need to raise up the front of your car using a car jack, and most of the weight will need to be retained on its wheels. You will need to get under the car, and a helper will need to turn its wheels from side to side so you can examine the movement. Unless you have wheel ramps that rest on a flat surface placed directly under each wheel, you will either require access to an inspection pit or have this done professionally. To carry out checks safely, you’ll need to firmly apply your handbrake, place chocks behind your rear wheels, then put the car in gear if it is a rear-wheel drive. If you have an automatic car, you’ll need to put it in park.
If you remove the rack and pinion system, there are several other ways to diagnose any problems with it. However, this is a fairly difficult procedure if you’re not an experienced mechanic, so it’s normally best to pass this problem off to a professional.
Potential Rack and Pinion Problems
Your car’s steering rack will be full of grease or oil. While this normally won’t be a problem, it may leak due to damage from grit or just from wear and tear over time. If your steering is stiff, this could be due to the rack having lost a lot of oil. You should try renewing the oil and cleaning the gaiters and rack before driving for a few miles to determine whether the stiffness has been resolved.
Another problem that may occur with your rack and pinion gears is cracking. If you spot any cracks, you will need to replace the rack as soon as possible. You should always inspect the teeth when you’ve turned the steering to full lock. You may be able to replace the gaiters yourself, as long as no grit has been able to get into the rack and damage it.
Checking the travel of your steering wheel can be done by marking the rim with chalk then using a finger as your reference point by which you can check the movement before your car’s front wheels start to move. Ask your helper to very slowly move the wheel until you tell them to stop. As soon as you observe the track rod moving, call out. If the steering wheel has moved over half an inch, you should check for any play at the ends of the track-rod and the steering rack. There shouldn’t be much play in your steering rack. You shouldn’t be able to move the rim of a steering wheel with a 15” diameter more than half an inch before the front wheels move. If it moves more than this, you’ll need to check the steering joints and ensure the rack has been securely properly by carrying out tests on the clamping bolts. When a steering wheel moves more than this distance your rack will either need adjusting or replacing. These are both jobs that should be done by your garage.
You may not be an expert on rack and pinion gears, but that doesn’t mean you should ignore them completely. They’re an essential part of the operation of most cars, and a little bit of know-how goes a long way towards ensuring that they stay in good shape—and that you’re able to diagnose and resolve any problems when they do occur.