How to replace the rear axle gearbox seal of a VAZ 2107

An oil leak from the axle gearbox through the drive gear oil seal is like a person with a runny nose. It seems that you are working as always, but this constant dampness under your nose is annoying. The only difference is that a person does not need the fluid flowing from the nose, but at the same time it is constantly produced by the body with a cold. And the bridge desperately needs the oil flowing out of the bridge, but it will not be able to replenish the supply without your help. It’s good that replacing the rear axle gearbox seal on a VAZ 2107 and other models of this series is possible with your own hands.

About the consequences of untimely “treatment”

And just as a runny nose can lead to serious problems in the body, even some kind of meningitis, oil leaking from the bridge can lead to serious “diseases” of the drive axle: overheating and jamming of bearings, scuffing on the surface of the gear teeth of the main pair, their rapid wear, increased noise and other troubles, including jamming of the main gear itself. Therefore, if you discover severe oiling in the area of the drive flange, or, even worse, an oil stain on the ground under the gearbox, you should not delay the “operation”. However, if “well, I can’t go on sick leave right now,” then by regularly monitoring and replenishing the oil level in the gearbox, the car can be operated for some time without any special consequences for the health of the bridge.

Assembly

Install the drive gear flange and washer.
Tighten the nut to a torque of 117-254 Nm. It can be determined more accurately by measuring the force of rotation of the gear. It should correspond to the value measured before removing the flange. When tightening the nut, it is necessary to hold the flange using a wrench, which can be made from a pipe with a pair of bolts and nuts attached to it.
Install axle shafts and wheels.
Fill the rear axle gearbox with new oil.

Good day, dear reader. Once you’ve entered the boat, it means you want to see the rear axle of your classic dry again, without fogging or oil leaks. This article tells you how to replace the rear gear oil seal (at the place where the crankshaft shank enters) on your own. First, let’s look at all the reasons why the VAZ rear gear oil seal stops holding oil.

A little anatomy

In the last years of its life on the AvtoVAZ assembly line, the classic Zhiguli remained perhaps the only passenger car in the world with a rigid drive axle. This design is simple and technologically advanced in production, but has serious disadvantages in operation:

large unsprung mass of the bridge, which negatively affects the smoothness of the vehicle;
tendency to steer when one of the wheels hits an obstacle - at this time, due to the misalignment of the bridge, both wheels tilt from the vertical and tend to roll in the direction of the tilt;
reduction in the useful volume of the trunk, because there must be free space between the axle and the car body for the axle to move during the compression of the suspension.

The advantage of a rigid axle, in addition to manufacturability, is its better adaptability to bad roads: the ground clearance under the axle practically does not change depending on the load, and the wheel drive is reliably protected from external influences by the axle housing.

The Zhiguli bridge consists of a stamped-welded bridge beam (such beams are called “Banjo” for their characteristic shape), a main gearbox with a differential, and axle shafts. The gearbox is made in a separate open housing, the flange of which is bolted to the crankcase. A drive gear with a driveshaft mounting flange and a differential with a driven wheel are mounted in the housing on bevel bearings. The main gears are hypoid, that is, their axes are located at an angle of 90 degrees to each other, but do not intersect (they are crossed). The amount by which the axis of the drive gear is offset relative to the axis of the driven gear is called hypoid offset. Such a transmission, if it is precisely manufactured and well adjusted, operates smoothly and with the least noise, but due to the intense sliding of the curved teeth, it is very sensitive to the quality and quantity of oil in the bridge.

The design of the bridge is relatively simple and technologically advanced, although it is not without its drawbacks

Differential device

The planetary gear is mounted on the differential housing. The differential consists of two axle gears, two satellites and a pin. The main, most common differential malfunctions are wear of the pinion pin (play) and wear of the splines on the axle gears.

On a car, the play of the pin of the satellites can be determined by turning the driveshaft by a quarter or more; if there is no play, then the shaft practically remains in place when you try to turn it in one direction or another.

It's also worth noting that there is never any noise coming from the differential. When moving forward (in a straight line), the differential rotates as one unit and it turns out that there is simply nothing to make noise there.

The cause of noise from the rear axle gearbox when gas is added and the noise disappears after releasing gas is (almost 99.9%) wear of the teeth of the main pair. This is clearly visible on the removed gearbox. The forward side of the teeth has significant wear, while the reverse side shows little wear.

If, after disassembling and troubleshooting the parts of the main pair, wear of the teeth is detected, then no repair will help and it will simply be a waste of time and money. Only the main pair needs to be replaced.

Can't you spoil the porridge with oil?

Oil is poured into the axle housing up to the lower edge of the filler hole, in the position when the axle is installed and secured to the vehicle. You should not fill oil above this level, since a larger volume significantly increases power loss when the gears rotate and provokes leaks.

Lubrication of gearbox parts occurs as follows. The lower part of the driven wheel and differential are constantly immersed in an oil bath. When the car moves, they rotate, alternately wetting with oil all the teeth of the main gear and differential gears. The differential bearings and the rear pinion bearing are lubricated in the same way. In addition, the teeth of the driven wheel spray oil abundantly, creating “oil mist” in the crankcase. The least amount of oil when splashed goes to the front, most distant, bearing of the drive gear. To lubricate it, a channel is made in the upper part of the crankcase, where, under the influence of centrifugal force, oil is thrown from the outer circumference of the driven wheel. The higher the rotation speed, the more oil enters the channel. This channel leads into the cavity between the bearings of the drive gear, passes through the bearings and returns to the bridge beam. To drain oil from the flange side of the drive gear, there is an oil drain channel in the crankcase. The bearings, due to the conical shape of the rollers, have a pronounced pumping effect, so the flow of oil that flows from the front bearing directly to the oil seal can be quite significant - more than one liter per minute. It is not easy to withstand such pressure, so an oil-removing washer is installed immediately behind the bearing, in front of the oil seal. It slows down the flow rate, but there is still a gap between it and the crankcase through which the oil flows to the oil seal. Therefore, the tightness of the drive gear oil seal is a constant concern for axle designers and manufacturers.

The amount of oil supplied to the oil seal depends on the speed of rotation of the driven wheel of the final drive

But the lack of oil supplied to the oil seal is no less, and perhaps even more harmful to its “health”, because with dry friction against the surface of the flange, no matter how smooth it may be in appearance, the working edge of the oil seal will wear out very quickly, and a gap will form between it and the shaft, through which not only oil can flow out, but also water can flow in if you need to cross a ford or just a deep puddle in a heavy downpour. And water in oil is a very quick “death” for gears and bearings.

When and why to change the front oil seal

The manufacturer recommends replacing the front crankshaft oil seal of VAZ 2101-2107 engines every 150,000 km. However, in practice such replacement has to be performed more often. Accelerated wear of the sealing element and the appearance of engine oil leaks are caused by:

skewed oil seal during installation;
loss of elasticity due to engine overheating;
increased radial runout of the drive pulley of mounted units;
use of low-quality motor oil;
wear on the crankshaft pulley hub.

In addition, we cannot rule out hardening of the cuff due to natural aging and the possibility of a manufacturing defect - unfortunately, the quality of parts for rear-wheel drive VAZ models leaves much to be desired.

It is impossible not to notice damage to the sealing element - the rotating pulley scatters oil in the front of the engine and throughout the engine compartment. However, do not think that such a malfunction only leads to oiling of the units and a decrease in the lubricant level. If engine oil gets on the generator belt and other rubber parts, it can quickly render them unusable.

Keep in mind that the appearance of a leak through the engine seals is provoked by another factor - increased crankcase gas pressure. For this reason, be sure to check the cleanliness of the engine ventilation system.

Something else useful for you:

Replacing the rear crankshaft oil seal of a VAZ 2101-2107 with your own hands
Replacing valve stem seals: main signs of wear, replacement procedure
DIY crankshaft bearing replacement for VAZ 2105-2107

Surgery or therapy?

So, our “wounded” axle is leaking oil around the drive gear flange, and we are ready to save it. But first, as is usual with serious doctors, you need to figure out the cause of the “disease.” How does an appointment with a local therapist usually begin? Of course, from measuring temperature and pressure. You may be surprised, but when starting to repair a bridge, we should also remember these physical characteristics. And that's why. During operation, the drive axle gets quite hot - the temperature in the crankcase can reach 80 degrees Celsius. And since, ideally, the axle housing is a sealed container, along with heating in a confined space, the pressure also increases. This is the law of physics. The increased pressure additionally loads all the seals and gaskets of the bridge, breaking out where, for some reason, there is less resistance. This is often the drive gear seal, which is subject to the most intense friction. To reduce pressure, a valve (breather) is installed on the axle housing, which releases excess pressure. Therefore, the first thing you need to start diagnosing a leak is by checking the functionality and cleaning the breather from dirt. The valve cap should rotate freely. When you lightly press the cap from above, it should move freely and return to its original state when the load is removed.

If cleaning the breather does not help, and the leak continues, it’s time to prepare “surgical instruments”. In our case, a regular plumbing kit will be enough, although it would be nice to grab another skein of thread and a hand balance scale (dynamometer) with a good scale.

Where is the gearbox located?

On the "sevens", as on all representatives of the rear-wheel drive family, the gearbox is located at the rear, under the bottom of the car. It connects the cardan to the VAZ 2107 axle and causes the wheels of the car to rotate. Rotation occurs thanks to axle shafts engaged in the gearbox, which, due to the technical features of the rear axle of the VAZ 2107, will have to be removed later. If the car is lifted, or when viewed from a garage pit, the gearbox is simply impossible not to notice.

Signs and malfunctions of the classic rear axle gearbox

Replacing a gearbox with your own hands is a labor-intensive process, which includes not only the purchase of a new unit (quite expensive), but also time costs. Therefore, before you start, you need to make sure that the gearbox is faulty. You can define the signs like this:

gradually accelerating the car, listen carefully and remember at what moment the noise appears;
while driving, start engine braking (remove your foot from the gas pedal at speed), at this time listen to the gearbox and note the moment the noise appears;
accelerate the "seven" to hundreds, switch to neutral and turn off the engine - listen to how the gearbox behaves while coasting.

“If the bridge is noisy both in neutral and at speeds, the gearbox has nothing to do with it. If the hum occurs only at speed (regardless of the number), repairs, or, as a last resort, replacement of the gearbox are inevitable.”

When the signs are identified, it is necessary to carry out another check:

park the car, secure the front wheels with shoes;
jack up the rear so that the bridge hangs over (it is necessary that the wheels come off the surface);
start the engine and accelerate the “seven” to the point at which noise occurs, while the wheels should spin without load.

If the noise has not changed, then the gearbox is clearly in good working order and it is not the cause of the trouble. Here other drive units are checked. Well, if there is no noise when driving without a load, then we are talking about worn gears of the gearbox, which make noise only when driving with a load.

The “seven” gearbox itself is a fairly reliable unit that can withstand a period of 100 to 300 thousand mileage, and there is no need to even look into it. Gears, gear spacer, differential adjustment - all these problems arise during improper operation:

the use of oil with a low viscosity level, as well as failure to comply with the terms of its replacement;
operating the “seven” with an amount of oil insufficient for this;
During movement, the bridge is subject to extreme loads (frequent and unsuccessful slips).

Gearbox removal process

In order to repair or replace the rear axle gearbox of a VAZ 2107, you first need to remove it from the car:

Drain the oil. This, by the way, may be a reason to replace it.
Separate the flanges of the cardan and gearbox. To do this, you need to unscrew four bolts and nuts. At this time, it is necessary to fix and immobilize the cardan with a screwdriver or by holding the brake pedal. After unscrewing the nuts, you need to tie the cardan to the muffler. You can simply hang it, but this can also lead to negative consequences for the cardan.
Remove the axle shafts, because without this the gearbox cannot be removed. At the same time, you can inspect the seals, and if they are worn out, replace them. This will save time and prevent possible malfunctions.
Separate the beam and gearbox by unscrewing all eight bolts that secure it. When unscrewing the latter, it is necessary to hold the gearbox so that it does not fall. The bolts are unscrewed - carefully remove the gearbox.

Repair and adjustment of the VAZ 2107 gearbox

Before you start repairing the gearbox and its subsequent adjustment, you need to have certain skills, backed up by skills, observe all the nuances and subtleties of this process, and also strictly follow the technological nuances of the process. Therefore, if a person starts work for the first time, then it is better to abandon this idea. In addition, you must have all the necessary tools:

pullers;
stands;
a set of keys, screwdrivers and other accessories.

Tell me, doctor, is there any way to do without surgery?

First of all, you need to drain the oil from the bridge. To do this, we turn out both plugs - both the drain and the filler. Next, disconnect the driveshaft from the bridge. When separating the axle and cardan flanges, be careful - sometimes oil accumulates in the cavity between the flanges. If this happens, then check the axial play of the flange by rocking it along the axis with your hand. There shouldn't be any play. If there is noticeable movement (in fact, play of more than 0.05 mm is already very harmful for the bridge), it is worth once again carefully inspecting the traces of oil on the crankcase. Perhaps the oil leaked not through the cuff, but through the gaps in the splines of the loose flange? In this case, it is worth trying to eliminate the play and observe the bridge in operation. If the leak stops, then that was the reason.

Axial play of the flange is eliminated by tightening the nut. When handling a flange nut, you should always remember that it does more than just hold the flange. This is the most important element in adjusting the drive gear bearings, and improper tightening can have serious consequences, ranging from noise to axle jamming. Having inserted two bolts into the holes of the flange, we insert the mounting between them so that, holding it, we prevent the rotation of the flange when the nut rotates. Pull the nut just enough to select the gap. The thread pitch is 1.25 mm, which means that when you turn the nut one turn, it will move along the axis by the same 1.25 mm. If the flange play is minimal - 0.05 mm, then it is enough to turn the nut 1/25 of a turn, that is, only 15 degrees.

Overtightening the nut loads the drive gear bearings with a large axial force, as a result they overheat and may fail. To be sure that we did everything correctly, we need to measure the moment of resistance to rotation of the drive gear. To do this, you need to remove the rear wheels and brake drums, unscrew the axle shaft mounting bolts and pull off the axle shafts, disengaging them from the differential gears. Then we tightly wind the thread onto the flange shaft and pull its free end with a steelyard, measuring the force at which the flange rotates evenly without jerking or acceleration. A less accurate result is obtained by another method, when the steelyard is hooked to a hole in the flange and also pulled evenly. In this case, care must be taken to ensure that the force is directed perpendicular to the radius of the flange circumference. You can also use a torque wrench, evenly rotating the drive gear shaft by the nut, but with such a movement it is difficult to follow its readings. We multiply the measured force value by the radius value, thereby obtaining the moment of resistance to rotation. The torque value should be in the range of 6–9 kgf.cm.

Torque wrenches usually have a scale marked in Newton meters (N.m). One kilogram-force per centimeter (1 kgf.cm) is equal to 0.098 newton meters, or approximately 0.1 N.m.

You can try to do without removing the axle shafts and measuring the torque on the flange. Experienced mechanics can do this. To do this, tighten the nut exactly until the play is eliminated and a little more. After this, we put the driveshaft in place and make a test drive in a mode sufficient for the bridge to warm up to operating temperatures (several tens of kilometers along a country road). After this, we check by hand the heating of the axle housing in the area of the drive gear bearings. If the hand tolerates heat, then we assume that everything is in order. If the bearings have become so hot that a drop of water on the crankcase hisses, then we have overdone it and now we definitely cannot do without a good adjustment. You cannot reduce the moment of resistance to rotation of the drive gear simply by loosening the nut. The fact is that a deformable spacer sleeve is installed between the bearings, which, when the nut is tightened, gives the structure the necessary rigidity. By tightening the nut, we compressed the bushing more than necessary, and it will no longer be able to lengthen back. When we loosen the nut, the bushing is no longer “spacer”, so it needs to be replaced. You should also pay attention to the bearings. If a blue color appears on the rolling surfaces, it means they have overheated and also require replacement.

How to replace a crosspiece

It is most convenient to change this with the driveshaft removed. Although, if the vehicle’s ground clearance allows it and there is no way to drive it onto a pit or overpass, then you can do it this way, especially in the case of trucks. You can also remove the shaft without a hole. Although it will take much more time, effort and nerves to repair. In the first case, the procedure will be as follows:

Following safety precautions, you need to block the wheels of the car. After this, you need to engage any gear (so that the driveshaft does not rotate).
Mark the location of all parts that will be removed relative to each other.
Unscrew the cardan bolts (secure the shaft to the axle flange). There are four of them.
Unscrew the suspension bearing mount (two nuts).
Pull the driveshaft out of the gearbox (there is a splined connection).

Once the shaft is removed, the universal joint spider can be removed. To do this, you will need pliers, a powerful flat-head screwdriver, a hammer and a round attachment (rod, tube). Its diameter should be slightly smaller than the diameter of the eyes in which the ends of the cross are secured. It will be much more convenient to work if you clamp the shaft in a vice.

Next you will need to do the following:

it is necessary to remove the fixing rings that hold the ends of the cross in the eyes. For this operation you need pliers. If the rings are too tight, then you should tap them with a hammer through the adapter so that the cups at the ends of the cross sag a little; After removing the rings, you need to knock the cups out of the eyes. This is done using the same attachment and hammer

It is important to remember that striking the cardan itself is not recommended. In the process of removing the cross in this way, the cup on which the blows are struck will sink inward, and on the other side of the fork the cup will come outward to a certain limit

In some cases, the cups may fall out on their own, but often they need to be pulled out using various suitable tools: pliers, a gas wrench, and so on. All four cups are removed in the same way; When the cross is removed, it is advisable to clean the lugs and the fork itself from dirt using a wire brush. It is recommended to go over the internal surfaces with sandpaper, clean the grooves of the retaining rings and wipe everything well from dust.

It should be separately added that there are special pullers for crosspieces. However, in practice they are used extremely rarely, even in repair conditions at large service stations. Let us add that no special tools are required when replacing the crosspiece, since installing a new part is also not difficult.

The two opposite cups can be easily removed by hand. You must act carefully so that the needle bearing does not crumble. It is important to pay attention to the presence of grease under the cup. The crosspiece is placed between the eyes on the shaft fork, after which the cups are put on. At this stage, they are easily recessed with your fingers as much as possible, and then, using a hammer and adapter, they are lowered so that the grooves of the retaining rings open. Retaining rings are installed. The same operation is performed with the other ends of the cross. Replacement of the cardan cross is complete. Now you can install it back.. As already mentioned, it is not always necessary to carry out this type of car repair

Sometimes lubrication is enough. This can be done without removal if a crosspiece with an oiler is installed - a special hole for introducing lubricant. There is nothing special about how to lubricate the cardan crosspieces. For this procedure you only need a special tool - a syringe. You can fill it with either a special lubricant for crosspieces, or use regular lithol

As already mentioned, it is not always necessary to carry out this type of car repair. Sometimes lubrication is enough. This can be done without removal if a crosspiece with an oiler is installed - a special hole for introducing lubricant. There is nothing special about how to lubricate the cardan crosspieces. For this procedure you only need a special tool - a syringe. You can fill it with either a special lubricant for crosspieces, or use regular lithol.

Let's go to the store

So we did everything we could, but the leak didn't stop. This means it's time to change the seal. Actually, according to GOST, these products are called “Reinforced rubber cuffs for shafts.” Or simply - cuffs. If a store offers you a part with that name, don’t be surprised. Factory part designation: 2101–2402052. Further, its variations can be written through a dash: -01, -02 and so on. All of these products are interchangeable and differ in the nuances of their design and manufacturer. Perhaps the most important thing when choosing an oil seal is the manufacturer. Choose products from well-known factories. No name details, in principle, should not attract your attention, because not only according to ours, but also according to Western standards, the cuff must be marked with the manufacturer’s trademark, cuff size, and type of material. Domestic GOST also provides for marking the year of manufacture. As a rule, these are two digits of the year when the mold was made, and next to them are dots, each of which indicates one year of operation of this equipment. You count the points, add their number with the numbers and find out in what year your part was manufactured. The year of manufacture is important because over time, any rubber compound “ages”, losing its shape and elasticity .

The type of mixture from which the oil seal is made is also important. The most expensive and most durable is fluorine rubber. It works well in aggressive environments and at high temperatures. It is usually marked with the Latin letters FBR. Nitrile butadiene rubber (NBR) is considered optimal in terms of price and quality for automobile transmissions. ACM acrylate polymer seals are also available, but they are usually used in components that should not be directly exposed to water. Chemists are constantly improving their products, so the fundamental differences between mixtures are becoming less and less, due to additives introduced into them that improve the weaknesses of certain recipes. Read reviews on the Internet, listen to the seller’s recommendations and make a decision based on your financial capabilities.

When examining externally, first of all pay attention to the quality of the working edge: it should be even and smooth around the entire circumference. You can use a magnifying glass. It will be a big plus for the gearbox seal to have an external boot - like a second edge, but without a spring and with a hole of a slightly larger diameter. The boot, as the name suggests, protects the work area from dust and dirt. The presence of an inclined notch on the boot or near the working edge indicates that the oil seal is designed for shafts rotating in the same direction.

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“Quiet, the operation is underway!” or Replacing the rear axle gearbox seal on a VAZ 2107

The sequence of work when replacing the gearbox seal is as follows:

We measure and record the moment of resistance to rotation of the flange (the axle shafts must be removed!) .
Unscrew the flange nut.
Remove the flange from the shaft splines.
Using expansion pliers, remove the oil seal. If you don't have pliers, you can pry it off with a screwdriver. Be careful not to damage the surface of the socket.
We inspect the flange. If its surface has a pronounced groove in the place where the working edge of the oil seal rubbed, then before installing the new oil seal, insert a washer 1 mm thick into the socket. If the flange is damaged on the working surface, replace it with a new one.
Lubricate the outer surface of the oil seal with lithol and carefully drive it into the crankcase socket using a mandrel of suitable diameter. If there is no mandrel, press in the oil seal by evenly tapping the end along the circumference of the outer diameter. Make sure that there are no distortions - the working edge should be strictly perpendicular to the shaft axis.
We inspect the lead-in chamfer on the flange. It should not have defects that could damage the working edge. We install the flange, avoiding sudden movements and impacts, so as not to knock the spring off the oil seal. Before installation, you can lubricate the flange chamfer with transmission oil to make the process easier.
We tighten the nut, periodically checking the moment of resistance to rotation of the flange. Remember that at the end of the tightening, the resistance in the bearings increases much more intensely than at the beginning . The moment of resistance to rotation should be 1–2 kgf.cm greater than what we recorded before unscrewing the nut. In any case, if the moment exceeded 9 kgf.cm, and the bearings in the bridge were still old, remove the flange again, take out the inner ring of the bearing and change the spacer sleeve. If the bearings are new (new means they have not traveled a single kilometer, because after a hundred kilometers they can be considered old for adjustment purposes), then the normal moment of resistance to rotation after tightening the nut for them should be in the range of 16–20 kgf. cm. Replacing the rear bearing will affect gear alignment, so please refer to the appropriate manual for this procedure .

To prevent self-loosening, the flange nut has a special plastic insert, which, when crushed against the thread, creates additional resistance both when screwing and unscrewing. As a rule, such nuts can withstand up to ten unscrewings without losing their locking properties. If in doubt, get a new nut.

We reinstall the axle shafts and brake drums, screw on the driveshaft, and fill in the oil. We make a test drive and if everything is in order, we enjoy life, until we suddenly find a treacherous spot under the bridge again...

Self-locking differential

The most common way to increase a car's cross-country ability is to install a self-locking differential. The main advantage of this device is that it prevents wheel locking “forever”. This is important because preventing lockup from engaging when not required helps protect the axle shafts from critical loads.

There are the following types of differential locks:

Disc - implemented through the use of friction clutches. These clutches come into action as soon as the wheels begin to rotate at an uneven speed. The disadvantage of this mechanism is that it requires the use of expensive gear oil, and also requires quite frequent adjustment work to set up the unit. This is far from the best mechanism for a VAZ 2107 car.
Viscous coupling blocking - the operation of such a device is based on the use of sticky discs immersed in a special liquid. It hardens when heated, allowing the gears to engage—that is, the differential locks. The liquid heats up when the angular speed of the wheels on the axle changes (when the speed of rotation of the wheels becomes different). The disadvantage of this mechanism is that they require complete sealing of the assembly, and work effectively only during short-term slipping.
Screw locking or worm locking is the best option for automatic locking for the VAZ 2107. The mechanism is implemented using worm screws, which rotate when the car drives in a straight line, and when the angular speed of the wheels changes, they shift into grooves, thereby locking the differential. As soon as the car gets out of the mud captivity, the blocked mechanism resumes its normal operation by moving the worm screws to their places.
Planetary - the operating principle is similar to a worm circuit, only instead of gears, balls are used. Due to the balls, the wheels are blocked, and they come into operation when the traction force between the engines and the axle changes. Compared to a self-locking worm gearbox, a planetary gearbox costs about 2 times less.

In addition to automatic differential locking, there is also a forced one, which is activated if necessary.

Important nuances

The dynamometer readings were mentioned above, and this is no coincidence. Tightening the flange is a very responsible process, and it can only be done using a torque wrench. This allows you to avoid excessive squeezing of the oil seal, which leads to a violation of the tightness of the entire gearbox. This is done like this: if at the first measurement the force on the dynamometer was 2.8 - 3 kg, then the force on the torque wrench when tightening should not exceed 6.3 kg. If the dynamometer showed 4.3 kg, then when tightening the key there should be no more than 9 kg, etc. If the dynamometer showed 2.7 kg, and the key when tightened shows 9 kg or more, it means that the gearbox adjusting sleeve is completely worn out and needs for urgent replacement.
After removal, the flange should be carefully inspected for severe abrasions and cracks. If there are any, the flange must be replaced. If this is not done, the new oil seal will very quickly become unusable.
Before driving the oil seal with a tube, it is recommended to lubricate it with lithol. This makes it much easier to fit the new oil seal into its original place.
When striking a pipe with a hammer, there is no need to be too zealous: with a strong blow, the pipe easily cuts the seal.

As you can see, replacing the oil seal itself does not take too much effort, and getting to it is not so difficult: just put the car in an inspection hole with good lighting. But tightening the flange so that it does not crush the new oil seal is a more difficult task. That is why the car owner needs a dynamometer and a special key, without which it is strictly not recommended to open the rear axle gearbox.