Rear axle VAZ 2107: repair, replacement. Which gearbox is better? Select "self-block"

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).

Repair and adjustment

Both repairs and subsequent adjustments require special skills and professional equipment; stands, pullers, special tools. Therefore, we will consider only the general principles by which repairs and post-repair adjustments of the gearbox are carried out in order to assess the required amount of work and the costs of purchasing spare parts.

The gearbox structure can be viewed in the following diagram:

Disassembling the gearbox begins with unscrewing the shank nut. After removing the flange, the drive gear with adjusting rings, oil seal, oil deflector, and inner bearing ring are removed. Then we press out the outer rings of the bearings. Lastly, the drive gear and differential are disassembled. When completely disassembled, the spacer sleeve is discarded.

It is not recommended to carry out the work described above related to disassembling the VAZ 2107 gearbox, due to its complexity. This is a rare case when you shouldn’t skimp on the services of specialists.

Most often, the bearings and the main pair of this unit fail, for which replacement with new ones is provided. It should be noted that it is the main pair that determines the gear ratio. There are three standard varieties of the main pair, with different gear ratios. The higher this number, the higher the power; the lower, the higher the speed of the gearbox. When replacing these parts, the spacer sleeve must be replaced, since it is disposable.

Some car enthusiasts use final drives as a way to tune their cars. By installing a main gear with a reduced gear ratio in the VAZ 2107 gearbox, they significantly increase the maximum speed of their car. In principle, the gear ratio can be selected for all rear-wheel drive cars without exception, guided only by your own needs. The gearbox of the VAZ 2102 had the largest gear ratio - 4.4. But after it was discontinued, finding a main pair with the same gear ratio became extremely problematic.

Repair is not advisable in all cases. For a rear axle gearbox that is too worn, it is more profitable to completely replace it with a new one. The difference in price will be compensated by the reduction in the cost of work performed by specialists and the durability of the new unit.

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.

Assembly procedure

After the repair has been completed and all the damaged elements have been replaced, it is necessary to reassemble the rear axle and make sure that the gearbox no longer makes noise when driving.
The process looks like this:

the new node is fixed in the place intended for it;
return the axle shafts to the bridge;
the gear flange is attached to the cardan;
install wheels and brake drives.

It is necessary to test the car both at low speeds and at high speeds. First of all, leaving the car in neutral gear, press the gas. Then accelerate smoothly, and then turn off the engine. In a situation where the noise is still heard, an unambiguous conclusion should be drawn: you made some mistake or the reason was not in the gearbox.

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 come in handy: How to change front suspension silent blocks

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

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.

Defects in the gearbox

Increased play in the RZM can be formed due to wear of the differential pinion pin - if you grab the driveshaft and rotate it clockwise and counterclockwise, this play can be felt. Also, increased clearance can be formed due to wear of the splines inside the differential housing itself.

If the gaps in the main pair of gearboxes are not adjusted, a characteristic noise occurs when the car moves:

when the load increases (sharp acceleration), a characteristic howl is heard in the bridge;
When I let off the gas the noise goes away.

“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. 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, it may be useful: Diagram of the brake system - its structure, principle of operation and malfunctions

Video: How to carry out work on a VAZ 2107

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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.