Rear axle VAZ 2107: features of operation and maintenance

The rear axle is a fairly reliable unit of the VAZ 2107, but despite its massive appearance, the mechanism requires regular maintenance, without which it can fail prematurely. This unit can serve for quite a long time if it is operated correctly and carefully, if possible avoiding extreme driving conditions of the vehicle. Calm and careful driving without sharp pressing of the gas and brake pedal, hard clutch engagement and similar overloads will contribute to the serviceability and durability of the rear axle.

• Specifications
• What is the rear axle made of?

  Frame

• Gearbox
• Half shafts

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.

Rear axle gearbox design of a VAZ-2107
If the axle is noisy both in neutral and at speed, 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).

Higher or lower?

Often, owners of classic Zhiguli cars use replacing the main pair as one of the types of tuning their cars. Which gearbox should I put on the VAZ-2107? It is worth choosing the gear ratio based on the engine power. If you install a pair with a low ratio (for Zhiguli the maximum parameter is 3.9), it will be easier for the car to accelerate to maximum speed. But in the range of 0-100 kilometers per hour, it will lose significant time for acceleration.

If the motor has not been modified, it is better to install a gearbox with a “4.4” ratio. The car will accelerate faster to one hundred kilometers per hour, but it will not go higher than this speed or will pick it up very slowly. Therefore, adjusting the gear ratios is not the only modification for the “seven”. In addition, the motor itself will have to be modified.

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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.

Adjustment and installation of the VAZ 2107 gearbox

Main pair engagement depth adjustments

In this case, it is necessary to select the thickness of the adjusting washer.

So: Instead of the device, we install the “original” shank and tighten the nut until it stops lightly, leaving a gap. The differential with planetary gear assembly, bearing caps are installed and their mounting bolts are tightened.

When replacing the shank oil seal, a number of incorrect actions are allowed, which ultimately lead to premature failure of the gearbox. Before releasing the shank nut, according to the technology for performing the work of replacing the oil seal, it is necessary to remove the axle shafts (which is almost never done, since the amount of work will increase many times). Although according to the price list, the removal of the axle shafts will most likely be included in the list and a fee will be charged for this, since this is required by the plant’s technology for replacing the oil seal. This is a necessary condition, since the axle shaft will create resistance when tightened and correct adjustment will simply be impossible to achieve.

Before releasing the shank nut, it must be secured against turning and the tightening force of the nut must be checked with a torque wrench, around 12 kgf. Before installing the oil seal, if its outer surface is not rubberized, then you need to use a sealant to guarantee it. Thus, a mark of 0.15 mm on the gearbox stocking will be sufficient to pass oil through the outer surface of the oil seal.

Back to assembly...

The adjusting nuts are installed, and the gap on the main pair is pre-selected (the final working gap is 0.08 to 0.12 mm). Then paint is applied to the teeth of the planetary gear from an aerosol can and, using a shank, it is necessary to make several movements in different directions in order to fix the contact spots in the paint.

Read, it may be useful: Replacing ball joints

Now, having turned the planet gear back, you can clearly see the contact patch on its teeth with the teeth of the pin. The contact patch (in this case) shows that the adjusting washer on the shank is thicker than the required thickness. We slightly tighten the shank nut, thereby moving its bearing, which makes it possible to move the gear teeth towards each other, that is, as if “reducing” the thickness of the adjusting washer. Using the differential bearing adjusting nuts, we set the approximate gap (reducing it slightly).

Then we again apply paint to the teeth of the planetary gear and again begin to rotate the shank (or gear) in different directions to print the contact patch between the teeth. It can be seen that the contact patch has risen a little, but still not enough and it is necessary to tighten the shank nut a little again. Similar actions with paint and turning the gear must be carried out until the contact patch is located exactly in the middle of the teeth, and the sound of the turning teeth becomes quieter.

After correct (final) adjustment, the sound will be almost inaudible.

Remember to tighten the differential bearing adjusting nuts every time you tighten the shank nut. As a result, the contact patch was located exactly over the entire surface of the teeth. It should be noted that this is the condition for the location of the contact patch for old (working) pairs. For new main pairs, the contact patch, as mentioned above, should be located in the center of the teeth.

Further. The planetary gear mounting covers are released and the differential is removed. The shank nut is unscrewed and removed. Since the shank was installed only with a bearing without an adjusting washer, there was a gap between the bearing and the shank gear where the washer would fit. This gap is measured with a set of feeler gauges, thereby calculating the required thickness of the adjusting washer.

It turns out, as in the case of using instruments and accessories, the size for the required adjusting washer was also 3.36 mm. The shank bearing is removed, an adjusting washer (3.36mm) is installed, the bearing is put in place and the gearbox is assembled. The shank is installed, the shank nut is tightened, min. 12 kgf. The differential with planetary gear is installed, the covers and bolts are tightened, but not completely.

By the way, the lids should not be mixed up. The adjusting nuts of the differential bearings are installed and the gap on the main pair is pre-set. Then the differential cover bolts are finally tightened. The gap in the main pair is finally adjusted and the adjusting nuts are secured.

The gearbox parts are assembled in the reverse order of disassembly. You can press in the bearing rings using a hammer and a special tool (a socket wrench head will do).

Adjusting the VAZ 2107 gearbox

Disassembling the unit

To disassemble the gearbox, you will need to do the following:

1. Unscrew the shank securing nut.
2. Remove the flange, then remove the drive gear along with the adjusting rings.
3. Remove the oil seal, inner race on the bearing and oil deflector.
4. Using a puller, remove the outer rings from the bearings.
5. Disassemble the drive gear along with the differential mechanism. Subsequently, the spacer sleeve must be replaced.

When disassembling the mechanism, be sure to mark the bearing caps so that they can be installed in the same way during reassembly. It is recommended to use a pencil or core to make marks. Label the right and left covers to avoid confusion during installation. It is advisable to mark these covers using a core.

Using a drift and a hammer, you need to remove the separator and the inner rings. Please note that you should not knock too hard. The rings are knocked out by lightly tapping in a circle. If you hit only one point, the ring will not come out. When repairing a rear gearbox, the bearings or the main pair are usually replaced. These are the most vulnerable elements of the system.

Checking the serviceability of the shank oil seal

The first sign that it is necessary to replace the shank oil seal on a VAZ 2107 is the presence of traces of lubricant, dust and dirt on the outer part of the rear axle. Determining the presence of leaks on the rear axle is not difficult. To do this, you need to climb under the car and inspect the bridge.

If the oil seal is worn significantly, a puddle of oil may be found under the car. If the problem is not resolved in a timely manner, oil may leak out of the bridge, which will lead to its rapid breakdown. Despite the fact that the cuff is a small part in a car, its serviceability plays a very important role.

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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:

1. We measure and record the moment of resistance to rotation of the flange (the axle shafts must be removed!).
2. Unscrew the flange nut.
3. Remove the flange from the shaft splines.
4. 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.
5. 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.
6. 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.
7. 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.
8. 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. Replacement of the rear bearing affects gear alignment, so please refer to the appropriate instructions 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...

Read this, it might come in handy: Instructions for bleeding the brake system

Video: How to carry out work on a VAZ 2107

Nut tightening

Now the most important point is tightening the nut. To properly tighten the nut, you need to do the following preparatory work:

1. hang up the rear of the car;
2. Remove the rear wheels and brake drums.

Tighten the nut until you feel a slight stop. Thus, we brought the bearings to the new spacer, but we had some play in the flange. He must be. This is normal with a new spacer. We tighten the nut 10-20 degrees and check the play. Tighten the nut until there is no play. Next, we check the force to break the flange using a digital scale. We insert the “ear” of the scale into the hole on the flange and pull it at a right angle. The breaking force should be within 1.5 kg. If the force is less than 1.5 kg, tighten the nut literally by degree and control the force.

The tightening torque of the nut should be from 12 to 26 kg/m when the required force is achieved. If, after eliminating the flange play, the force is significantly more than 1.5 kg, then you have received a defective spacer sleeve.

Next we reassemble:

1. We fasten the cardan according to the marks;
2. Fill in new oil (you need to pour oil with API GL-4/GL-5 approvals, volume 1.5 liters);
3. We install brake drums and wheels.

The process of replacing the rear axle gearbox seal of a VAZ 2107 is clearly shown in this video:

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:

1. 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.
2. 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.
3. 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.

4. 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.