What is a driveshaft: key features

Every owner of a car with all-wheel drive or rear-wheel drive will sooner or later encounter a drive shaft malfunction. This transmission element experiences heavy loads, which is why it needs frequent maintenance.

Consider the peculiarity of the operation of this part, in which nodes the cardan is used, how is it arranged, what are the malfunctions and how to service it?

What is a driveshaft

Cardan is a mechanism that transfers rotation from the gearbox to the rear axle gearbox. The task is complicated by the fact that these two mechanisms are located in different planes with respect to each other. All models of cars, the rear wheels of which are driving, are equipped with cardans.

The transmission cardan is installed along the exhaust system of the car and looks like a long beam going from the gearbox to the rear axle. It is equipped with at least two cross joints (one on each side), and in nodes with a small displacement of the axes - one.

A similar gear is also used in the steering system of a car. A hinge connects the steering column to a steering gear located in a different plane.

In agricultural machinery, such a device is used to connect additional equipment to the tractor power take-off shaft.

From the history of the creation and use of the cardan

As most motorists know, only rear- and all-wheel drive car models are equipped with a propeller shaft. For vehicles with front-wheel drive wheels, this part of the transmission is simply not needed. In this case, the torque is transmitted directly from the gearbox to the front wheels. For this, the gearbox has a main gear, as well as a differential (about why it is needed in the car, and how it works, there is separate detailed review).

For the first time, the world learned about the principle of cardan transmission from the Italian mathematician, engineer and doctor Girolamo Cardano in the 16th century. The device, named after him, came into use at the end of the 19th century. One of the first auto developers to take advantage of this technology was Louis Renault.

Renault cars equipped with a cardan drive received a more efficient transmission. It eliminated the dips of torque in the process of transferring it to the rear wheels, when the vehicle got on an unstable road. Thanks to this modification, the transmissions of the cars became softer while driving (without jerking).

Over the decades of modernization of vehicles, the principle of cardan transmission has remained intact. As for the design of such a transmission, depending on the car model, it can be very different from its related counterparts.

Propeller shaft device

The following elements are included in the cardan mechanism.

1. The central shaft. It is made of hollow steel pipe. Void is necessary to facilitate construction. On one side of the pipe there are internal or external slots. They are required to install a sliding fork. The hinge fork is welded on the other side of the pipe.

2. The intermediate shaft. In multi-sectional modifications of the cardan, one or more of these elements are used. They are installed on rear-wheel drive cars to eliminate the vibration that occurs when a long pipe rotates at high speeds. On both sides fixed forks of hinges are fixed on them. In sports cars, one-section driveshafts are installed.

3. The crosspiece. This is an element of the hinge with tips, inside which is located a needle bearing. The part is installed in the eyes of the forks. It transfers rotation from the driving fork to the driven. Additionally, they provide unobstructed rotation of two shafts, the angle of which does not exceed 20 degrees. In the case of a larger difference, another intermediate section is installed.

4. Outboard bearing. It is mounted in an additional section mount. This part fixes and stabilizes the rotation of the countershaft. The number of these bearings is identical to the number of intermediate sections.

5. Sliding fork. It is inserted into the central shaft. When the car is moving, the distance between the bridge and the gearbox is constantly changing due to the shock absorbers. If you fix the pipe tightly, on the very first bump you will need to change some kind of knot (the one that will be the weakest). This may be a break in the shaft mounting or failure of the bridge parts. The sliding fork is equipped with slots. Depending on the modification, it is either inserted into the central shaft (corresponding grooves are made inside it), or is worn on top of the pipe. Slots and grooves are needed so that the pipe rotates the hinge.

6. Hinge forks. They connect the central shaft to the intermediate. The flange plug has a similar shape, only it is installed at the place of attachment of the entire mechanism in front to the gearbox, and at the rear to the axle gearbox.

7. Flexible coupling. This part softens the shock of the universal joint when it is shifted while riding. It is installed between the flange of the output shaft of the box and the plug-flange of the central shaft of the cardan.

What function does it perform?

The main objective of this mechanism is the transmission of rotational movements on axes located in different planes. The gearbox is located higher than the rear axle of the car. If you install a straight beam, due to the displacement of the axes, it either breaks itself or breaks up the nodes of the box and bridge.

Another reason why this device is necessary is the mobility of the rear axle of the machine. It is fixed on shock absorbers, which move up and down when driving. In this case, the distance between the box and the rear gear is constantly changing. A sliding fork compensates for such differences without loss of torque.

Types of drivelines

Basically, most motorists associate the concept of cardan transmission with the operation of the rear-wheel drive transmission. In fact, it is used not only in this auto node. The steering and some other mechanisms that connect to neighboring ones at different angles work by a similar principle.

There are 4 types of gears:

1. asynchronous;
2. synchronous;
3. flexible half;
4. semi-cardan hard.

The most famous type of cardan gears is asynchronous. The main application is in transmission. It is also called transmission with a hinge of unequal angular velocities. Such a mechanism consists of two forks, which are connected by a cross at a right angle. Tips with a needle bearing allow the crosspiece to move smoothly in accordance with the position of the forks themselves.

This hinge has one feature. It transmits an uneven indicator of torque. That is, the rotation speed of the connected shafts is periodically different (for a full revolution, the secondary shaft overtakes two times and lags behind the main one twice). To compensate for this difference, another hinge is used (on the opposite side of the pipe).

How asynchronous transmission works is shown in the video:

Drive shaft operation. Work propeller shaft.

Synchronous transmission is equipped with a constant velocity joint. Owners of cars with front-wheel drive are familiar with this device. A constant velocity joint connects the differential to front wheel hub. Sometimes they are equipped with transmissions of more expensive four-wheel drive cars. Compared to the previous type, synchronous transmission is less noisy, but more expensive to maintain. SHRUS provides the same speed of rotation of two shafts with an angle of inclination of up to 20 degrees.

Flexible half-cardan transmission is designed to rotate two shafts, the angle of which does not exceed 12 degrees.

In the modern automotive industry, rigid semi-cardan transmission is rarely used. In it, the hinge transmits torque when the shaft tilt angle is shifted to two percent.

There is also an indoor and outdoor type of cardan gear. They differ in that the cardans of the first type are placed in the pipe and more often consist of one hinge (used in trucks)

Checking the condition of the propeller shaft

Check the cardan in the following cases:

• during acceleration, additional noise appears;
• an oil leak appeared near the checkpoint;
• knock when shifting gear;
• at speed, increased vibration is transmitted to the body.

Diagnostics must be carried out by lifting the car on a lift or using jacks (for how to choose the appropriate modification, see separate article) It is important that the drive wheels can rotate freely.

Here are the nodes to check.

• Mount. The intermediate support and flange joints must be tightened with a bolt with a lock washer. If it is missing, the nut loosens, resulting in backlash and excessive vibration.
• Elastic coupling. It often fails, since the rubber part compensates for the axial, radial and angular displacements of the parts to be joined. You can check for a malfunction by slowly turning the central shaft (in the direction of rotation and vice versa). The rubber part of the coupling must not be torn or loosen at the place where the bolts are fastened.
• Sliding fork. The free lateral movement in this assembly appears due to the natural wear of the spline joint. If you try to rotate the shaft and the coupling in the opposite direction, and at the same time there is a slight backlash between the fork and the shaft, then this assembly must be replaced.
• A similar procedure is carried out with hinges. A large screwdriver is inserted between the eyes of the forks. It plays the role of a lever, with the help of which they try to crank the shaft in one direction or the other. If backlash is observed during rocking, the cross must be replaced.
• Outboard bearing. Its serviceability can be checked by taking with one hand the shaft in front of it, and with the other - behind it and shaking it in different directions. In this case, the intermediate support must be firmly fixed. If play is noticeable in the bearing, the problem is solved by replacing it.
• Balancing. It is performed if the diagnosis does not reveal any malfunctions. This procedure is performed on a special stand.

Here is another video that shows how to check the gimbal:

Suspicious sounds in the area of ​​the universal joint, vibration, etc.

Propeller shaft service

According to the recommendations of the manufacturers, the cardan is serviced after 5 thousand kilometers. In this case, it is necessary to check the elastic coupling and crosspieces. If necessary, wear parts are replaced with new ones. Slides of the sliding fork are lubricated.

If a cardan with serviced cross pieces is installed in the machine, they must also be lubricated. This modification is determined by the presence of grease in the universal joints of the cardan (hole for connecting an oil syringe).

Cardan shaft malfunctions

Since this mechanism is in constant motion, and it experiences heavy loads, malfunctions are often encountered with it. Here are the most common ones.

• Oil appeared on the cardan shaft. It is necessary to pay attention to the gearbox oil seals. They must be changed periodically due to normal wear and tear. Elastic gaskets lose their properties over time and small gaps appear between the shaft and the gland. If a leak appears in the area of ​​the sliding fork, you need to check the condition of the splines. If they have roughness, then the plug must be replaced.

• Shocks during cardan loads are caused by play on the joints. If the free play appeared in the crosses or in the bearing of the pendant mount, then these parts are replaced with new ones. Vibration may occur due to loosening of the bolted joint. In the event of a frequent occurrence of such a problem, you should check whether the Grover is installed between the nut and the mount. This washer prevents the nut from unscrewing with constant vibration.

• Squeaks when you press the accelerator pedal. Check joints. Due to constant contact with moisture and dirt, the cross may fail. If you ignore the creaks, the crosspiece will jam and the joint will break.

• The most common drive shaft malfunction is vibration. But before proceeding with the repair of the mechanism, you should first check the chassis. Impaired wheel balancing also leads to the appearance of vibration at high speeds. If this effect disappears when shifting and another gear, then the cardan has nothing to do with it. Here are the reasons why vibration can occur in the universal joint:
  • malfunction of balancing rings (corrosion or break);
  • destruction of crosses;
  • damage to the central or intermediate shaft (deformation of the pipe leads to an imbalance of the mechanism);
  • incorrectly assembled components of the mechanism.
• Ringing in the pipe. Behind the spline connection inside the pipe there is a cover that prevents grease from entering the shaft. To fix the breakage, the pipe is cut, the lid is welded into place, then the shaft is welded. If after the procedure there was a ringing of a different nature (as if a stone was in the shaft cavity), it means that after welding work there was a large scale. A clipping of lead support may lead to ringing. In this case, the problem is fixed by installing a new cardan.
• Rattle when gear is engaged. Occurs in contact with a car body or exhaust system.
• The ringing of the cardan itself may appear due to a breakdown in the mounting of the mud reflector (if any). It is mounted on an intermediate support to protect the bearing from water and dirt. If it hangs, just weld it by welding.

Oil leak

A special grease is used to lubricate the joints. Usually, for CV joints, needle-type bearings, spline joints, an individual grease is used that has the desired characteristics.

So that dirt does not get into the cavity of rubbing or rotating elements, they are protected by anthers, as well as oil seals. But in the case of parts located under the bottom of the car, this protection is only temporary. The reason is that the protective covers are constantly in the zone of active aggressive action of moisture, dust, and in winter, also chemical reagents, which are sprinkled on the road.

If the car often moves over rough terrain, then there is an additional risk of damaging such protection with a stone or a branch. As a result of damage, an aggressive environment begins to act on rotating and longitudinally moving parts. Since the propeller shaft constantly rotates during the movement of the vehicle, the lubricant in it heats up, and as the oil seals wear out, it can leak out, which over time will lead to a breakdown of this part of the transmission.

Vibration during acceleration and knocking at the checkpoint

This is the first symptom by which a malfunction of the propeller shaft is determined. With a slight wear of the rotating elements throughout the body, they spread throughout the body, as a result of which there is an unpleasant hum in the car while driving. True, for some car models, this acoustic effect is a completely natural factor by which the presence of a propeller shaft in the transmission is determined. This is especially true for some old domestic cars.

Creak during acceleration

The squeak that appears at the moment of acceleration of the vehicle determines the wear of the crosspieces. Moreover, this sound does not disappear, but rather amplifies during the acceleration of the car.

The squeak in this part is emitted by the needle bearing rollers. Since they are least protected from the aggressive effects of moisture, over time, the bearing loses its lubrication and the needles begin to rust. When the car accelerates, they get very hot, expand, begin to vibrate and make a strong creak.

Due to the high torque, the crosspiece is subjected to heavy loads. And the revolutions of the crankshaft are not synchronous with the speed of rotation of the wheels of the car. Therefore, squeaking may appear regardless of the speed of the vehicle.

Outboard bearing problems

As we learned from the subtopic on the design of the propeller shaft, the outboard bearing is a conventional bearing with round rollers enclosed in a rosette. To prevent the device from breaking down due to constant exposure to dust, moisture and dirt, the rollers are protected by plastic covers, and there is thick grease inside. The bearing itself is fixed under the bottom of the car, and a cardan pipe passes through the central part.

To prevent vibrations from the rotating pipe being transmitted to the body, a rubber sleeve is installed between the outer race and the bearing mounting bracket. It acts as a damper to minimize the acoustic effect during the operation of the driveline.

Although the bearing is sealed and filled with grease that cannot be added or replaced in any way (it is filled at the factory during the manufacture of the part), the cavity between the rosettes is not sealed. For this reason, over time, in whatever conditions the car is operated, dust and moisture gets inside the bearing. Because of this, there is a depletion between the rollers and the loaded part of the socket.

Due to the lack of lubrication (it gradually ages and is washed out), rust can appear on the bearing rollers. Over time, the ball, which has been severely damaged by corrosion, disintegrates, due to which a large amount of foreign solid particles appears inside the bearing, destroying other elements of the part.

Usually, with such a bearing failure, a howl and hum appears. This element needs to be replaced. Under the influence of moisture and aggressive chemicals, the rubber coupling ages, loses its elasticity, and subsequently crumbles due to constant vibrations. In this case, the driver will hear distinct strong knocks transmitted to the body. It's not worth driving with such a breakdown. Even if the driver is willing to put up with a lot of noise in the cabin, due to the large offset, the propeller shaft can be severely damaged. Moreover, it is impossible to predict which of its parts will break first.

Consequences of improper operation of the cardan

As we have already noticed, problems with the cardan are primarily recognized by the increasing noise and decent vibrations coming to the body while the vehicle is moving.

If the driver is distinguished by iron nerves and incredible calmness, then ignoring vibrations and strong noise due to a worn propeller shaft will certainly lead to unpleasant consequences. The worst thing that can happen is the breakage of the shaft while driving. This is especially dangerous and always leads to accidents when the shaft breaks at the front of the machine.

If signs of cardan problems appear while driving, the driver should reduce speed and stop the vehicle as soon as possible. Having indicated the place where the car stopped, it is necessary to carry out a visual diagnosis of the car. Here's what you need to pay attention to:

• For all bolted connections;
• On the condition of the outboard bearing, especially on its rubber damper;
• On the condition of the flanges;
• On crosses;
• On the bearing caps.

It is not recommended to disassemble the shaft on your own either on the road (to replace a broken part) or in a garage if the car owner does not have the appropriate skills. Cardan repair should always be accompanied by its balancing, which cannot be done in the conditions of road repair.

For these reasons, the condition of this part of the transmission must be monitored. Scheduled technical inspection and, if necessary, repairs are the key to the proper and safe operation of any car system and its units, including the propeller shaft.

Removing and installing propeller shaft

If there is a need to replace the cardan mechanism or repair its assembly, it will need to be removed. The procedure is carried out in the following sequence:

• unscrewing mounting bolts from the rear axle and propeller shaft flanges;
• the shaft goes down;
• bolts of the rubber coupling are unscrewed;
• the cardan moves away from the checkpoint;
• pendant mount is unscrewed.

A repaired or new mechanism is installed in the reverse order: suspension, coupling, bridge flanges.

In an additional video, some more subtleties of removing and installing the cardan are mentioned:

Drive shaft patriot | removal and installation | flange replacement

Cardan in the car is a fairly hardy mechanism, but it also needs periodic maintenance. The driver needs to be attentive to the appearance of extraneous sounds and vibrations. Ignoring these problems will break important transmission elements.

Finding a new propeller shaft

If there is a need for a complete replacement of the propeller shaft, then finding a new part is a simple procedure. The main thing is that there is enough money for it, since this is a rather expensive part in the transmission of some car models.

To do this, you can use the auto disassembly services. But in this case, you need to be sure that the company selling used parts is trustworthy and does not sell low-quality products. In some localities, there are firms that restore parts that are subject to complete replacement and sell them at an affordable price, but after a short period of time these elements fail.

It is much safer to search the catalog of an online store or at a physical point of sale - an auto parts store. In this case, it is necessary to search for a spare part according to the exact data of the car (make, model, date of manufacture, etc.). If some information about the car is not available, then all the necessary data can always be found by the VIN-code. Where he is in the car, as well as what information about the vehicle it contains, is told in a separate article.

If the part number is known (the marking on it, if it has not disappeared during operation), then the search for a new analogue in the catalog can be performed using this information. In the case of purchasing components for disassembly, then before buying you need to pay attention to:

1. Condition of fasteners. Deformations, even minor ones, are the reason why the part is not worth buying. This is especially true for such cardan shafts, the design of which does not provide for the installation of a flange;
2. Condition of the shafts. Although it is difficult to check this parameter visually, even minor deformations (including lack of balancing) will lead to strong vibration of the shaft, and subsequent breakdown of the device;
3. The state of the spline connection. Corrosion, burrs, notches and other damage can seriously affect the performance of the driveline;
4. The condition of the outboard bearing, including the elasticity of the damper part.

Regardless of whether the gimbal looks serviceable on disassembly or not, it must be shown to a specialist. The professional immediately recognizes whether the gimbal was understood or not. In the event of repair work with this unit, a specialist will be able to say whether the structure was assembled correctly.

And one more important point. Even if you buy a used product, the products covered by the warranty (either from the manufacturer or from the seller) are worthy of attention.

Related videos

Finally, watch a short video on what you can do to prevent the propeller shaft from vibrating:

PROPELLER SHAFT SO THERE IS NO VIBRATION !!!

Questions and answers:

Where is the propeller shaft. The propeller shaft is a long beam that runs from the gearbox along the exhaust system of the vehicle to the rear axle. The cardan shaft device includes a central shaft, crosses (their number depends on the number of nodes between the shafts), a sliding fork with a splined connection, and a thrust bearing.

What is a gimbal. Under the cardan is meant a mechanism that provides the transfer of torque between shafts, which are located relative to each other at an angle. For this, a cross is used that connects the two shafts.