Steering Gearbox: Removal, Replacement or Repair, Assembly and Installation with Your Own Hands, What Oil to Lubricate the Steering Gear

In the vehicle control system, the steering gear transmits and amplifies torque from the steering wheel. Structurally, it is a mechanical transmission placed in a housing, fixedly mounted on the car body, and has its own lubrication and adjustment system.

Steering gearbox

A trackless ground vehicle is basically useless without the turning function. It is responsible for the steering system, consisting of a wheel (steering wheel), a column, a gearbox and an actuator (traction to the steered wheels, usually the front ones). The algorithm for turning the car looks like this:

the driver applies force to the steering wheel;
torque is transmitted to the column (shaft inside a tubular structure);
then the steering gear changes the spatial position of the rotation axis, increases the torque, and transmits it to the rocker;
The middle and side rods, hinged on the rocker, push the steering arms of the steered front wheels in a given direction.

Operating principle of a steering system with gearbox

In other words, the steering gearbox converts the rotation of the steering wheel into reciprocating left/right movements relative to the vehicle's path, making it possible to turn the vehicle.

This principle can be implemented in several ways, the most popular of which are gear/worm, screw/rack and pinion/rack.

Attention: The last gear does not have a housing, that is, it is not a full-fledged gearbox. Will not be covered in this guide.

Rack and pinion steering

Oil is poured into the steering gear to lubricate friction parts only in worm and screw versions with a crankcase.

The purpose of the gearbox in the steering system of a car

the driver applies force to the steering wheel;
torque is transmitted to the column (shaft inside a tubular structure);
then the steering gear changes the spatial position of the rotation axis, increases the torque, and transmits it to the rocker;
The middle and side rods, hinged on the rocker, push the steering arms of the steered front wheels in a given direction.

Operating principle of a steering system with gearbox

In other words, the steering gearbox converts the rotation of the steering wheel into reciprocating left/right movements relative to the vehicle's path, making it possible to turn the vehicle.

This principle can be implemented in several ways, the most popular of which are gear/worm, screw/rack and pinion/rack.

Attention: The last gear does not have a housing, that is, it is not a full-fledged gearbox. Will not be covered in this guide.

Rack and pinion steering

Oil is poured into the steering gear to lubricate friction parts only in worm and screw versions with a crankcase.

Pros and cons of steering gear

The advantages include the self-braking effect, large gear ratios due to the use of only two parts, low noise levels and smooth running.

The disadvantages of a worm-type steering gear are increased wear, excessive heat generation due to friction forces, jamming and relatively low efficiency. To prevent jamming and rapid wear, it is necessary to adjust the mechanisms and comply with assembly accuracy requirements.

The main advantage of a worm gearbox over a gearbox is that the initial contact of the links occurs along a line, rather than at a point. The input and output shafts in a worm-type steering gearbox can be crossed at different angles (most often at 90°). Another significant advantage is that with the same gear ratio, the worm gear takes up much less space.

Gearbox design

In a simplified form, the steering gear design represents a mechanical gear transmission with a gear ratio of 15 - 30. This makes it possible to reduce the torque force that the user must apply to the steering wheel. The main nuances are:

with an increase in the gear ratio, it is much easier to turn the shaft inside the steering column;
at the same time, the angle through which you need to turn the steering wheel deviates to a larger direction;
at high speeds this is dangerous for an accident, since the driver may not be physically able to cope with this task.

Gear ratio

In this regard, in vehicles with hydraulic booster or electric power steering (power steering and electric power steering, respectively), these units duplicate the reduction in torque on the steering wheel. For example:

in a gearbox with a gear ratio of 30, to turn the wheels by 25 degrees, the steering wheel must be unscrewed by 750 degrees;
a gear with a ratio of 15 will require a 375 degree rotation of the steering wheel to achieve similar wheel rotation;
however, in the first case, 6 kN of force must be applied, and in the second, 3 kN, which is half as much.

Gearbox for 2 steering turns

Vehicle designers put a scheme into the gearbox - from a neutral position (wheels in the direction of travel) within 2.5 turns of the steering wheel, they must turn 30 - 45 degrees to the left or right at most. That is, the total stroke of the steering wheel will be 4–5 revolutions, so that the bearing will last longer and the user will have comfortable control at different speeds.

Spatial position

The steering column is located vertically or obliquely, and the rods and levers of the rotary wheels are horizontal, so the simplest option for converting rotation is a horizontally located gearbox - a rack.

In all other cases, that is, when using gearboxes (transmission in a housing), vertical modifications are used:

the worm, lower bevel gear or screw are located vertically;
The slide mounted on their shaft rotates in a horizontal plane.

Vertical gearbox

In complex circuits, an angular steering gear usually transmits rotation from cardan to cardan, and then to the control mechanism. Accordingly, each gearbox uses a different bearing design.

Angular reducer

Attention: Power steering and electric steering do not belong to steering gearboxes, as they are independent complex components of the car.

Power steering design

Transmission type

Gear and worm gears are traditionally considered the most effective. However, they can use bevel, spur and combination gears. There are kinematic diagrams of gearboxes of several modifications:

single-stage, two-stage, multi-stage;
with split steps;
with deployed coaxial steps.

Mercedes multi-stage gearbox

The most commonly used schemes are:

gear – worm (worm);
bevel gear – bevel gear (angular);
screw – ball nut – rack – gear (screw).

Screw reducer

Executive-class passenger cars, heavy trucks and buses are equipped with screw mechanisms. Worm modifications are installed on other cars; they are not sensitive to uneven road surfaces; the gear is in constant mesh and provides greater maneuverability.

By default, the worm has a larger contact surface with the shaft, the bearing experiences less load, and is operated in a gentle mode. In helical gearboxes, the shaft and bearing wear out faster.

In practice, the worm can be mated with a two-tooth or multi-tooth crank, a 2-5 tooth sector and a roller with two or three ridges. Most machines use a globoid worm rather than a cylindrical worm (saddle-shaped work surface). This allows you to reduce friction by 15 - 25%.

Regular and globoid worm in gearbox

Gear ratio

This characteristic is strictly tied to the design of a particular vehicle. Cars with steering racks are considered the most maneuverable, but the steering wheel has to be turned with noticeable tension, which is especially noticeable on old VAZs that are not equipped with an electric steering and power steering.

With an average gear ratio U=20, a full turn of the steering wheel corresponds to a wheel turn of 20 degrees. Currently, for trucks and buses the accepted value is U 20 - 25. For example, for LiAZ it is 23.6 according to the passport, and for KamAZ it is exactly 20.

Man Truck Steering Gearbox

For passenger cars, the standard is conventionally considered to be U in the range of 16 - 20. For example, the VAAZ 2105 has a gear ratio of 16.4 units. The main nuances of the steering are:

As the design becomes more complex, the play in the steering wheel increases, as parts wear out and tightening is not done in a timely manner;
at low speeds and when taxiing out of a parking lot, more force is required on the steering wheel, which is why mechanisms with variable gear ratios have been created;
there is feedback - jerking of the steering wheel when moving on uneven road surfaces and rough terrain.

Since the unit is critical and quite complex, the steering gearbox is sold with an instruction manual, which indicates how to adjust the free play and force on the steering wheel for a specific design.

What can be made from a steering gear

It is worth mentioning what can be made from a steering gear, since its scope is not limited to installation in cars. A winch is a very useful thing; it can be used to lift heavy loads and pull out stuck cars. If you still don’t have it, but you still have a gearbox you don’t need, this is a great way to combine the necessary and the useful.

The process of creating a winch from an unnecessary gearbox is quite interesting, but its detailed consideration is worthy of a separate topic. Most suitable for the manufacture of worm-type parts. Before you start creating a winch, you should find out what the steering mechanism is and what it is used for in cars and electrical engineering.

Steering gear location

Since under the hood of a car there is the main “culprit” of vibrations – the engine, the steering gearbox is attached exclusively to the car body. Its location differs among different brands and modifications, but access to the fastener is always extremely difficult.

Gearbox location in Jeep WJ Limited

To adjust the steering gearbox, you will have to remove the protection from below, at a minimum. Driver injury safety in a frontal collision is ensured in the following way:

the upper mounting bolts are welded to the gearbox housing;
At the bottom there are tear-off bolts, the edges of the fixing plates of which pass into special slots in the bracket.

Breakaway bolts for driver safety

When impact occurs, the steering wheel folds forward upward, which is safer for the driver's chest than any other option.

What is the steering gear used for on a VAZ?

Many car owners in the domestic auto industry are interested in the question of why the steering gear is suitable for a VAZ and how to determine this. There is no definite answer to this question, since everything depends on the length of the shaft. It usually differs for different car models. Therefore, when moving the gearbox from one car to another, it may be necessary to replace the steering column with a suitable one.

Another way to solve the problem is to purchase a new gearbox. This can be done at any auto parts store or online. To do this, you should find out in advance what the car part number looks like and what it is or how to find it on a removed gearbox. By using this number you will protect yourself from purchasing the wrong part.

Basic faults

Depending on the design and operating conditions of a particular car, repair of the steering gear becomes necessary when malfunctions are detected:

tight steering wheel rotation, increased feedback;
creaks, knocking and oil stains in the parking area;
A breakdown is considered to be a deterioration in the controllability or maneuverability of the machine.

Manufacturers recommend minimal do-it-yourself repairs - you can change the seals and lubricant, knowing what oil or packing to use, and adjust the gaps. It is better to correct other faults in the service.

Knock in the gearbox

Knocking in a car is an unpleasant and annoying thing, and there can be several reasons for the source of the noise, so it is sometimes difficult to determine the original source of the problem. If you hear a clear knocking or clicking sound in the gearbox when turning the steering wheel, then try adding transmission oil; perhaps its level has completely dropped. It would be good to completely change the oil. This operation should be performed once every 2 years or every 30-40 thousand km. The level is checked using any clean rod inserted all the way.

The gearbox must first be wiped to prevent dirt from entering. Next, unscrew the oil channel cap and pump out the old oil with a syringe. Any transmission oil is suitable for replacement. Pump it up to a mark of 15-20 mm from the neck. The knocking should now go away. If the knocking noise remains, this is due to wear on the steering gear worm or bearing, which will have to be replaced.

Adjustment

Unlike repairs, steering gear adjustment can be done on your own. To do this, manufacturers provide an adjusting screw in the design, usually protected by a polymer cap or plug.

Bevel gear adjustment screw

By rotating it, the gap between the transmission parts (roller/worm, sector/worm, bevel gear/bevel gear) increases or decreases, depending on the design of the gearbox being used:

the protective cap is removed, the lock washer is removed after loosening the nut;
the steering wheel is quickly turned by an assistant at a small angle of about 15 degrees to the right/left;
at the same time, the master removes the free play by unscrewing or tightening the screw with a screwdriver;
the steering force and free play are brought into the optimal ratio in the specified way;
When tightening the nut, you must hold the screw slot in the adjusted position with a screwdriver.

Adjusting the free play and steering force with a screw

Attention: Play may be present in the axis of the pendulum arm; tightening another nut located on the top of this axis, protected from twisting by a cotter pin, will help get rid of it.

Pulling the nut of the pendulum arm axle

By analogy with this, a knock in the steering gear can be caused by loosening of the intermediate shaft fasteners, swing arm nuts, pendulum arm bracket, or crankcase fasteners. A similar effect is caused by an increase in clearance in worm bearings or in the worm/roller mesh itself.

Basic requirements for steering

There are standard requirements that apply to the steering system. If the system meets these requirements, it can be considered operational.

Steering wheel free play angle. This is the turning angle that is done “idle”, before the wheels begin to turn. Normally for passenger cars it should be no more than 10 degrees, and if the free play gradually increases, this indicates the need for adjustment or repair.
The system must “steer” correctly! That is, it is normal to keep the car when driving in a straight line, to perform maneuvers accurately, and not to deviate from the given trajectory.
The steering wheel should turn easily during maneuvers. Amplifiers were invented for this purpose, so that on the road the driver would think about the road, and not about whether he has enough strength for the next turn. If control is tight and requires significant effort, the problem needs to be found and solved.
Strictly adjusted number of full rotations of the steering wheel from the middle to the extreme position. To make a turn, the driver does not have to twist the steering wheel indefinitely.
The system should work even after the power steering is turned off. Anything can happen on the road, including a hydraulic fluid leak or a failure of the electric motor in the power steering unit. At the same time, the car must maintain controllability. Yes, it will require more effort, but the stop will be where the driver wants.

Lubrication

Experienced users often change the lubricant, even in the absence of breakdowns, for the following reasons:

The standard blue padding is too thick;
Possible decrease in plasticity in winter;
it accumulates near the lid and minimally reaches the friction pairs.

Standard gearbox lubrication

Usually a graphite lubricant with the addition of engine oil for dilution or a special gear packing is used.

Graphite grease with Motul 4100 10W40

Some cars, for example, VAZ 21213 Niva, use transmission oil, as indicated in the official manufacturer's manual for the service station. To do this, the upper crankcase cover has a hole protected by a threaded plug; oil can be added without disassembling the gearbox.

VAZ 21213 gearbox with lubrication hole

Repairing leaks

If the steering gear grease periodically remains on the asphalt under the car, the causes of the malfunction may be:

worm and bipod shaft seals - a repair kit is required at a price of 1200 - 3500 rubles, depending on the design of the gearbox;
the shaft near the steering bipod is worn out - the part is considered not repairable, in practice we repair it by welding and subsequent grinding in the factory;
deformation of the lower cover of the worm shaft bearing - return to the initial geometry.

Gearbox leak

In any case, you will have to remove the steering gear, which is very difficult in practice. On some cars it is removed upwards after partial dismantling of other components and mechanisms in the engine compartment (for example, the injector assembly). In others, it is unscrewed from the top and pulled out downwards; at a minimum, a hole will be required and the removal of the engine protection.

Design and principle of operation of the steering gear

All gearboxes have a housing made of cast iron or welded steel. The housing contains transmission elements - gears, shafts, bearings, etc. Sometimes the gear housing may contain devices for lubricating bearings and gears.

Today, there are many types of gearboxes known. They can be classified: by type of transmission (worm and gear); by type of gears (bevel, cylindrical, bevel-cylindrical); by the number of stages (single-stage, two-stage, etc.); depending on the features of the kinematic scheme (with a deployed coaxial scheme or with a bifurcated stage); depending on the location of the shafts in space (horizontal, vertical).

With all the variety of designs, cars are most often equipped with worm gearboxes. Such gearboxes transmit torque using a worm gear, the main elements of which are a worm screw and a toothed worm wheel. Worm gears are used in all steering gears today.

The worm is a special screw made of durable materials and having a trapezoidal thread profile. A worm wheel is very similar in appearance to a regular gear wheel, but the threads on such a wheel are carefully adjusted to the shape of the threads of the mating worm. Typically, gears for heavy-duty worm gearboxes are made from two different materials. The raw material for the core is any inexpensive and at the same time durable steel (or ordinary cast iron), and the teeth are made of high-strength anti-friction materials. Due to its design, the worm gear is effective in applications that require high torque combined with low angular velocity.