Rear axle gearbox on VAZ 2107: design, repair, replacement

Torque from the gearbox is transmitted to the rear wheels of the “seven” through the rear axle gearbox. The gears installed in the gearbox wear out over time and begin to make noise when moving. In this case, you will have to change or repair the rear axle gearbox of the VAZ 2107.

Signs of a malfunction of the rear axle gearbox of the VAZ 2107

The gearbox is a fairly expensive part, and its repair is a labor-intensive and complex process. Therefore, you should first make sure that the cause of the noise is a gearbox malfunction. You can do this as follows:

• Choose a flat section of the road and gradually accelerate on it from 20 to 90 km/h. While driving, you should listen carefully and note the appearance and disappearance of extraneous noise from the rear axle gearbox.
• Release the gas and start braking with the engine. While the speed is decreasing, you should also note the moments when noises appear and disappear.
• Accelerate the car to approximately 100 km/h and, switching to neutral, turn off the engine. While the car is coasting, note the presence and disappearance of noise.

To verify the presence or absence of a mono problem like this:

• Park the car, securing it with wheel chocks.
• Raise it with a jack, hanging the rear axle.
• Start the engine, turn on the speed and add gas so that the wheels rotate without load, and the speedometer shows the same speed as during tests on the move.

If the noise remains the same when operating without load as under load, the problem is not in the gearbox. Other rear-wheel drive components should be checked.

If the gearbox does not make noise without load, you will have to start restoring it. Worn gears begin to make noise only under load.

Purpose and principle of operation of the gearbox

The rear gearbox of the “seven” is a transmission link between the axles of the rear wheels and the engine. Its purpose is to transmit torque from the engine crankshaft to the rear wheels while simultaneously converting the rotation speed of the axle shafts.

Rear gearbox - transmission link between the engine and the rear wheels of the “seven”

In addition, the gearbox must be able to distribute torque depending on the load applied to the left or right wheel.

Principle of operation

Here are the main stages of transmitting torque from the motor to the gearbox:

• the driver starts the engine and the crankshaft begins to rotate;
• from the crankshaft, torque is transmitted to the car’s clutch discs, and then goes to the input shaft of the gearbox;
• when the driver selects the desired gear, the torque in the gearbox is transferred to the secondary shaft of the selected gear, and from there to the driveshaft connected to the gearbox with a special crosspiece;
• the cardan is connected to the rear axle gearbox (since the rear axle is located far from the engine, the “seven” cardan is a long rotating pipe with crosses at the ends). Under the action of the cardan, the main gear shaft begins to rotate;
• rotating, the gearbox distributes torque between the axle shafts of the rear wheels, as a result the rear wheels begin to rotate.

Removing the rear axle gearbox of VAZ 2107

Before removing the gearbox, it is necessary to drain the transmission oil that is poured into the rear axle of the VAZ 2107. To do this, place an oil container under the drain hole of the axle and unscrew the drain plug.

Important: after repair, new transmission oil should be poured into the gearbox.

The next procedure is as follows:

• Unscrew the bolts securing the cardan to the gearbox flange;
• Uncouple the rear part of the cardan and lower it down;
• jack up the car (if it is not on a lift) and remove the rear wheels;
• Unscrew the guide screws of the brake drums;
• remove the brake drums;
• unscrew the 4 bolts securing the axle shafts;
• pull out the axle shafts, freeing the gearbox;
• unscrew the 8 gearbox mounting bolts;
• remove the gearbox.

Device

In order for the car to move, it is necessary to transfer the rotation of the engine to the wheels. But the engine speed is too high, and in order to correctly distribute the torque, a mechanism is needed that changes the gear ratio. Due to the gearbox and different engine speeds, the speed of movement changes, and the main pair of the rear axle takes over the rotation and transmits it to the wheels through gears.

The VAZ rear axle gearbox consists of the following parts:

• flange, it is fixed on the drive gear (shank) of the RZM, and is an intermediate link between the driveshaft and this gear;
• the shank of the main pair, at one end of which there are splines for pressing the flange, at the other end there is a bevel gear with a small number of teeth;
• driven gear (planet gear), it is in mesh with the drive gear, and it is with it that it forms the main gear;
• center differential, allowing the rear wheels to spin at different angular speeds.

The differential design is very simple - the mechanism consists of two axle gears, two satellites and a satellite pin. From the gearbox, the movement is transmitted to the axle shafts, on which the wheels are mounted.

Repair and adjustment of the VAZ 2107 gearbox

Adjusting and repairing the gearbox requires some skills and careful adherence to technology. It is also necessary to have pullers, stands and special tools. If the above is not the case, you should entrust the work to professionals.

If your qualifications are insufficient, it is better not to start working with the gearbox. Assembly and adjustment work requires fairly high metalworking skills. It is not difficult to disassemble the VAZ 2107 axle, but this is one of the few components of the “Seven” that requires highly qualified maintenance. It is not worth saving on these works.

Disassembling the gearbox is performed in the following sequence:

• unscrew the shank nut;
• remove the flange and remove the drive gear and adjusting rings;
• remove the oil seal, oil deflector, inner ring of the bearing;
• press out the outer rings of the bearings with a puller;
• disassemble the drive gear with the differential (the spacer sleeve in this case must be replaced).

When disassembling the gearbox, it is necessary to put marks on the bearing caps in order to then install them in their original position. To do this, you can use a core (which is more reliable) or a pencil. Marks must be placed on the covers and on the body, so that later during assembly they can be aligned. You should also mark the left and right covers so as not to confuse them.

This can be done this way: on the covers, in addition to the marks opposite the marks on the body, apply numbers or letters with a pencil. The disadvantage of this method is that the marks will be erased when you clean the lid. Therefore, it is safer to simply make marks with a core. For example, one on the left cover and two on the right.

The inner rings with the separator are removed using a hammer and drift. You need to knock out the rings by lightly tapping them in different places. If you hit only one place, you won’t be able to pull out the ring.

Typically repairs consist of replacing bearings or the main pair. These parts most often fail.

The main pair is available in several variations and determines the gear ratio. The higher the gear ratio, the greater the traction; the lower, the higher the maximum speed of the machine. There are three standard versions of the main pair, used on different VAZ models.

VAZ 2107 owners sometimes install the main gearbox pairs with a non-standard gear ratio. To increase traction, pairs are set with a larger value, to increase maximum speed - with a smaller one. If the task is to tune a car, you can take this opportunity to change these characteristics of the VAZ 2107.

Reference: the VAZ 2102 axle had the maximum gear ratio (4.44). After this model was discontinued, finding pairs with this ratio became problematic, but as practice shows, the best option is installation on a VAZ 2107 with a 1.5-1 engine ,6 gearboxes with 2103 (4.1 gear ratio). When choosing this gearbox in conjunction with a five-speed gearbox, traction and speed are maintained.

Repairing the rear axle gearbox of a VAZ 2107 is not always advisable. It is often easier to replace the gearbox with a new one. It is worth considering that the new unit will be more durable than the restored one.

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.

Home-couple

The gears of the main pair are selected at the factory based on contact patch, noise and other parameters and are marked. For example, on the planetary gears it is stamped - VAZ 2103 (model), 10 41 (gear ratio), 4091 (pair number). The main pair number 4091 is also marked on the bevel gear.

After marking these parts, they became the “main pair” and are not installed one without the other, that is, “family”. “- 6” is also marked on the “tip”; this is an amendment for assembling the main pair in the gearbox. When troubleshooting a differential, its bearings are also checked for wear and, if necessary, replaced. Bearing wear is often caused by unprofessional replacement of the gearbox seal.

For example, after replacing the oil seal, tighten the shank nut without observing the tightening torque (pull as much as possible) and the force is transferred not to the spacer sleeve, but to the differential bearings.

As a result, after a short run after replacing the shank oil seal, noise from the gearbox appears. Only in this case, the “hum” noise in the gearbox is constant and unlike the noise from worn teeth of the main gear. In this case, the hum is constant, regardless of whether gas is added or released.

Rear axle gearbox assembly video

During assembly, the gearbox is adjusted according to 4 parameters:

1. Selection of the adjusting ring

Parameters from 2.6 to 3.5. The ring serves to adjust the depth of engagement of the teeth of the “tip” and “planetary gear”, which is strictly specified. This is where the “correction -6” is needed for this main pair, which was mentioned above. Of course, this amendment will be individual for each main couple.

In this video, the main pair will be adjusted using a special device. It is clear that the vast majority of motorists do not have such a device and this is just a clear example of adjusting the engagement depth parameter. An option will also be given for adjustment without a “device”.

A “device” with a micrometer is also installed on the device, simulating the gear of the main pair. The indicator shows zero. Then the indicator leg is transferred to the bearing bed and in this case the indicator shows a value of 3.25, which is not good, since it should be within the range of 3.0. On the second landing plane it turned out to be 3.45. The arithmetic mean is 3.3. To adjust, we will use the correction at the “tip” - “-6”. In this case (– 3.3) + (-6) = 3.36. The thickness of the adjusting washer required is 3.36 mm. Using a micrometer, select the washer of the required thickness.

Note. When the shank bearing wears out, it begins to rotate on the “tip” body. As a result, the bearing end, adjusting washer and shank gear bodies wear out. It turns out that when replacing the shank oil seal, even with the correct tightening torque, the adjustment of the depth of engagement of the teeth of the gears of the main pair is lost and the “howl” of the pair is ensured, as is its early failure.

Adjustment and installation of the VAZ 2107 gearbox

Before assembling the gearbox, all parts must be thoroughly washed in kerosene. They should be inspected before installation. Gear teeth should not be chipped or scored and have the color of metal, and not be covered with a black coating of oil. Minor scuffs on the satellite axle, journal and axle gear seats can be treated with fine sandpaper. If there are large scuffs or large wear, the parts must be replaced.

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).

The gaps between the gears of the gearbox are adjusted using an adjusting ring, the thickness of which is selected individually. For selection, you need a caliper and probes of various thicknesses. The flange nut must be tightened with a torque of 18 kgf-m.

Adjusting the VAZ 2107 gearbox

Disassembling the gearbox and replacing satellites

The satellites are additional gears installed in the differential gearbox. Their purpose is to transmit torque to the axle shafts of the rear wheels. Like any other part, pinion gears are subject to wear. After this, they will have to be changed, since this part cannot be repaired. To restore worn teeth, the car owner has neither the necessary skills nor the necessary equipment. In addition, any gear in a car undergoes a special heat treatment - carburization, which is carried out in a nitrogen atmosphere and strengthens the surface of the teeth to a certain depth, saturating this surface with carbon. An ordinary car enthusiast cannot do anything like this in his garage. Therefore, there is only one solution: purchase a repair kit for the rear axle gearbox. It costs about 1500 rubles. Here's what it includes:

• a pair of gears for axle shafts;
• a pair of satellites for the differential;
• satellite axis;
• support washer.

In addition to the repair kit for gearboxes, you will also need a set of regular open-end wrenches, a screwdriver and a hammer.

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.