Tips for checking and replacing the CV joint and its anther

Many motorists are aware that their car has a part called a CV joint, but not everyone knows what it is and what it is for. The cunning abbreviation stands for the hinge of equal angular velocities. But for most people, decoding explains little. In this article, we will try to figure out the purpose and device of the CV joint, find out how to check and replace this part.

What is it and what does it serve

In the early days of the automotive industry, engineers faced serious difficulties in trying to implement front-wheel drive. At first, universal joints were used to transfer rotation from the differential to the wheels. However, in conditions where the wheel during movement is shifted vertically and at the same time also turns, the outer hinge is forced to work at an angle of the order of 30° or more. In a cardan drive, the slightest misalignment of the mating shafts leads to uneven angular velocity of rotation of the driven shaft (in our case, the driven shaft is the axle shaft of the suspension). The result is a significant loss of power, jerks and rapid wear of the hinges, tires, as well as the shafts and gears of the transmission.

The problem was solved with the advent of joints of equal angular velocity. CV joint (in the literature you can sometimes find the term “homokinetic joint”) is an element of an automobile, thanks to which the constancy of the angular velocity of each axle shaft is ensured, regardless of the angle of rotation of the wheels and the relative position of the drive and driven shafts. As a result, torque is transmitted with virtually no power loss, without jerking or vibration. In addition, CV joints allow you to compensate for the stroke and vibration of the motor while driving.

In shape, the CV joint resembles the well-known ammunition, which is why it got its common name - “grenade”. However, some prefer to call it a "pear".

Two CV joints are installed on each axle shaft - internal and external. The inner one has a working angle within 20 ° and transmits torque from the gearbox differential to the axle shaft. The outer one can work at an angle of up to 40°, it is installed at the end of the axle shaft from the side of the wheel and ensures its rotation and rotation. Thus, in the front-wheel drive version there are only 4 of them, and the all-wheel drive car has 8 “grenades”.

Since the right and left axle shafts have structural differences, then the CV joints are right and left. And of course, internal and external hinges differ from each other. This must be taken into account when purchasing new replacement parts. Do not forget also about the conformity of the installation dimensions. Anthers also need to be selected in accordance with the model and modification of the machine.

Structural varieties of CV joints

The equal angular velocity joint is not a new invention, the first samples were developed about a hundred years ago.

double gimbal

First, they began to use a double cardan CV joint, consisting of two cardan joints working in pairs. It is able to withstand significant loads and work at large angles. The uneven rotation of the hinges is mutually compensated. The design is quite bulky, so in our time it has been preserved mainly on trucks and four-wheel drive SUVs.

Cam

In 1926, the French mechanic Jean-Albert Gregoire invented and patented a device called the Trakta. It consists of two forks, one of which is connected to the drive shaft, the other to the driven shaft, and two cams joined together. Due to the large contact area of ​​the rubbing parts, the losses turned out to be very high, and the efficiency was low. For this reason, cam CV joints are not widely used.

Cam-disc

Their modification, cam-disc joints, developed in the Soviet Union, also had a low efficiency, but withstood more significant loads. Currently, their use is limited mainly to commercial vehicles, where high shaft speeds are not required, which can lead to excessive heating.

Weiss ball joint

The first constant velocity ball joint was patented in 1923 by Karl Weiss. In it, the torque was transmitted using four balls - one pair worked when moving forward, the other when moving backward. The simplicity of design and low cost of manufacture made this device popular. The maximum angle at which this hinge operates is 32 °, but the resource does not exceed 30 thousand kilometers. Therefore, after the 70s of the last century, its use practically disappeared.

Alfred Zeppa's ball joint

More fortunate was another ball joint, which not only successfully survived to this day, but is also used in almost all modern front-wheel drive and many all-wheel drive vehicles with independent suspension. The six-ball design was invented in 1927 by Polish-born American engineer Alfred Hans Rzeppa, who worked for the Ford automobile company. In passing, we note that on the Russian-language Internet the name of the inventor is written everywhere as Rceppa, which is absolutely wrong.

The inner clip of Zheppa's CV joint is mounted on the drive shaft, and the bowl-shaped body is connected to the driven shaft. Between the inner race and the housing there is a separator with holes holding the balls. There are six semi-cylindrical grooves at the end of the inner cage and on the inside of the body, along which the balls can move. This design is highly reliable and durable. And the maximum angle between the axes of the shafts reaches 40°.

CV joints "Birfield", "Lebro", GKN are improved versions of the Zheppa joint.

"Tripod"

The hinge called “Tripod” also comes from “Zheppa”, although it differs from it quite a lot. A fork with three beams located at an angle of 120° relative to each other is placed inside the body. Each beam has a roller that rotates on a needle bearing. The rollers can move along the grooves on the inside of the housing. The three-beam fork is mounted on the splines of the driven shaft, and the housing is connected to the differential in the gearbox. The range of working angles for the “Tripods” is relatively small - within 25 °. On the other hand, they are very reliable and cheap, so they are often put on cars with rear-wheel drive or used as internal CV joints on front-wheel drive.

Why such a reliable part sometimes fails

Careful drivers rarely remember CV joints, only from time to time they replace their anthers. With proper operation, this part is able to work out 100 ... 200 thousand kilometers without problems. Some automakers claim that the CV joint resource is comparable to the life of the car itself. This is probably close to the truth, however, some factors can reduce the life of the constant velocity joint.

• The integrity of the anther is of paramount importance. Due to its damage, dirt and sand can get inside, which will act as an abrasive that can disable the “grenade” in just a couple of thousand kilometers or even faster. The situation can be aggravated by water together with oxygen if they enter into a chemical reaction with the additive contained in the lubricant in the form of molybdenum disulfide. As a result, an abrasive substance is formed, which will accelerate the destruction of the hinge. The average service life of anthers is 1 ... 3 years, but their condition should be checked every 5 thousand kilometers.
• The fact that a sharp driving style can ruin a car in record time is probably known to everyone. However, the number of extreme sportsmen is not decreasing. A sharp start with the wheels turned out, fast off-road driving and other excessive loads on the suspension will destroy the CV joints much earlier than their allotted time.
• The risk group also includes cars with a boosted engine. CV joints and drives in general may not be able to withstand the additional load resulting from increased torque.

• Particular attention should be paid to lubrication. Over time, it loses its properties, so it must be changed periodically. Only one that is specifically designed for CV joints should be used. In no case do not stuff graphite grease into the “grenade”. Improper lubrication or insufficient lubrication will shorten the life of the CV joint.
• Another reason for the premature death of the “grenade” is assembly errors. Or maybe you were just unlucky, and the part turned out to be initially defective.

How to check the condition of the CV joint

The first step is to inspect and make sure that the anther is not damaged. Even a small crack is the basis for its immediate replacement, as well as flushing and diagnosing the “grenade” itself. If this procedure is carried out in time, it is possible that the hinge can be saved.

A faulty CV joint makes a characteristic metallic crunch. To check, try to make a turn at a large angle. If it crunches or knocks during a right turn, then the problem is in the left outer hinge. If this occurs when turning left, the right outer “grenade” probably needs to be replaced.

Diagnosis of internal CV joints is easiest to carry out on a lift. After starting the engine, engage 1st or 2nd gear. The steering wheel must be in the middle position. Listen to the work of the internal CV joints. If a crackling sound is heard, then the hinge is not in order.

If a crunch is heard while driving in a straight line, and acceleration is accompanied by vibration, the defective joint should be replaced immediately. Otherwise, it may soon completely collapse. The likely result is wheel jamming with all the ensuing consequences.

How to replace correctly

A defective CV joint cannot be repaired. The part will have to be replaced entirely. The exceptions are anthers and their clamps, as well as thrust and retaining rings. It should be borne in mind that the replacement of the anther involves the mandatory dismantling, washing and troubleshooting of the hinge itself.

Replacement is a labor-intensive task, but quite feasible for those who have experience in auto repair and want to save money. The process may have its own nuances depending on the specific car model, so it is better to be guided by the repair manual of your car.

To carry out work, the machine must be installed on a lift or inspection hole and partially drain the oil from the gearbox (1,5 ... 2 l). Of the tools, a hammer, a chisel, pliers, a screwdriver, wrenches, as well as a mount and a vise will come in handy. Consumables - clamps, special grease, hub nut - usually come with a new "grenade". In addition, WD-40 or another similar agent may be useful.

Never remove both shafts from the gearbox at the same time. Complete one axle first, then move on to the other. Otherwise, the differential gears will shift, and great difficulties will arise with the assembly.

In general, the procedure is as follows.

1. The wheel is removed from the side where the hinge will change.
2. The hub nut skirt is punched with a hammer and chisel.
3. The hub nut is unscrewed. To do this, it is better to use a pneumatic wrench. If such a tool is not available, then you will have to work with a ring wrench or head. Then you will need to press and lock the brake pedal to immobilize the wheel.

4. Unscrew the bolts that secure the lower ball joint to the steering knuckle. is retracted downwards, and the steering knuckle is moved to the side.

5. The outer CV joint is pulled out of the hub. If necessary, use a soft metal drift. Sometimes parts stick to each other due to rust, then you need WD-40 and a little patience.

6. The drive is released from the gearbox. Most likely, it will not work manually because of the retaining ring at the end of the inner “grenade” shaft. A lever will help - for example, a mount.
7. The shaft is clamped in a vice and the CV joint is knocked off it. You need to hit with a soft drift on the bearing (inner race), and not on the body.
8. The removed “grenade” is thoroughly washed with gasoline or diesel fuel. If necessary, the part should be disassembled and troubleshooted, then lubricated with special grease and reinstalled. If the CV joint changes completely, then the new joint must also be washed and filled with grease. Approximately 80 g is required in the external one, 100 ... 120 g in the internal one.
9. A new anther is pulled onto the shaft, after which the “grenade” is mounted back.
10. The clamps are tightened. A special tool is needed to securely tighten the band clamp. If not, then it is better to use a screw (worm) clamp or a plastic tie. First tighten the large clamp, and before installing the small one, use a screwdriver to pull the edge of the boot to equalize the pressure inside it.

After tightening the hub nut, it should be punched so that it does not subsequently unscrew.

And don't forget to put the grease back into the gearbox.