We independently repair the rear axle gearbox on the VAZ 2107

The VAZ 2107 car is equipped with rear-wheel drive. This technical solution has both advantages and disadvantages. The key element of the "seven" drive is the rear axle gearbox. It is this device that can deliver a lot of problems to the car owner due to poor adjustment or due to banal physical wear and tear. The motorist can fix problems with the gearbox on their own. Let's figure out how it's done.

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 rotational speed of the axle shafts.

Rear gearbox - the 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 transferring torque from the motor to the gearbox:

• the driver starts the engine and the crankshaft starts to rotate;
• from the crankshaft, the torque is transmitted to the clutch discs of the car, 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 cardan shaft 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;
• while rotating, the gearbox distributes the torque between the axle shafts of the rear wheels, as a result, the rear wheels also begin to rotate.

The device and technical characteristics of the gearbox

The rear gearbox of the VAZ 2107 car consists of a massive steel casing with a shank, a cardan shaft flange, two final drive gears mounted at right angles to each other and a self-locking differential.

The main elements of the gearbox are the housing, the main pair of gears and the differential with satellites.

Rear gear ratio

The main characteristic of any gear is its gear ratio. It is the ratio of the number of teeth on the driven gear to the number of teeth on the drive gear. There are 2107 teeth on the driven gear of the rear gearbox VAZ 43. And the drive gear has 11 teeth. Dividing 43 by 11, we get 3.9. This is the gear ratio on the VAZ 2107 gearbox.

There is another important point to be noted here. VAZ 2107 was produced for many years. And in different years, gearboxes with different gear ratios were put on it. For example, the earliest models of the "sevens" were equipped with gearboxes from the VAZ 2103, the gear ratio of which was 4.1, that is, the ratio of the teeth there was 41/10. On later "sevens" the gear ratio changed again and was already 4.3 (43/10) and only in the newest "sevens" this number is 3.9. For the above reasons, the driver often has to independently determine the gear ratio of his car. Here's how it's done:

• the car is set to neutral;
• The rear of the car is raised with two jacks. One of the rear wheels is securely fixed;
• after that, the driver manually begins to turn the cardan shaft of the machine. It is necessary to make 10 turns;
• by rotating the cardan shaft, it is necessary to calculate how many revolutions the unfixed rear wheel will make. The number of revolutions of the wheel should be divided by 10. The resulting number is the rear gear ratio.

Подшипники

The rotation of all gears of the gearbox is provided by bearings. In the rear gearboxes of the VAZ 2107, single-row roller bearings are used on the differential, and the rollers there have a conical shape. Bearing marking - 7707, catalog number - 45–22408936. The price of a bearing on the market today starts from 700 rubles.

All bearings of the rear gearbox of the “seven” are roller, single-row, conical

Another bearing is installed in the gearbox shank (i.e., in the part that connects to the universal joint). This is also a tapered roller bearing marked 7805 and catalog number 6-78117U. Standard VAZ liner bearings today cost from 600 rubles and more.

Planetary pair

The main purpose of the planetary pair in the rear gearbox of the VAZ 2107 is to reduce the engine speed. The pair reduces the crankshaft speed by about 4 times, that is, if the engine crankshaft rotates at a speed of 8 thousand rpm, then the rear wheels will rotate at a speed of 2 thousand rpm. The gears in the VAZ 2107 planetary pair are helical. This decision was not chosen by chance: a helical gear is almost twice as quiet as a spur gear.

The planetary pair has a helical gear to reduce noise

But helical planetary pairs also have a minus: gears can move along their axes as they wear. However, this problem is relevant for racing cars, in the rear axles of which there are exclusively spur gears. And on the VAZ 2107 for all the years of production of this car there were exclusively helical planetary pairs.

Typical gear failures and their causes

The rear gearbox VAZ 2107 is a reliable device that is very resistant to mechanical wear. However, over time, parts gradually wear out even in the gearbox. And then the driver begins to hear a characteristic crunch or howl that is heard in the area of ​​\uXNUMXb\uXNUMXbthe rear axle or in the area of ​​​​one of the rear wheels. Here's why it's happening:

• one of the wheels jammed, as one of the rear axle shafts was deformed. This happens extremely rarely, usually after a strong blow to one of the wheels. In this case, the semi-axle is deformed so much that the wheel cannot rotate normally. If the deformation is insignificant, then the wheel will rotate, however, during rotation, a characteristic howl will be heard due to the damaged wheel. It is not possible to fix such a breakdown on your own.. To straighten the axle shaft, the driver will have to turn to specialists;
• crunch in the gearbox when the car is moving. This is a more common problem that every driver of the old "seven" will face sooner or later. The gearbox begins to crackle after several teeth and splines on the axle shafts wear out in the main gear. With very strong wear, the teeth can break. This happens both due to metal fatigue and poor gearbox lubrication (this is the most likely reason, since the lubricant in the “seven” gearbox often leaves through the breather and through the shank flange, which have never been tight). In any case, such a breakdown cannot be repaired, and gears with broken teeth will have to be changed;
• axle bearing wear. This is another reason for the characteristic rattle behind the wheel. If the bearing has collapsed, then you cannot drive such a car, since the wheel may simply fall off while driving. The only solution is to call a tow truck and then replace the worn bearing. You can do this both on your own and in a service center.
  

  If the bearing on the axle shaft is worn out, the vehicle cannot be operated

About gear adjustment

If the driver finds out that the main pair of gears in the rear axle is completely worn out, he will have to change this pair. But just changing the gears will not work, since there are gaps between the gear teeth that will have to be adjusted. Here's how it's done:

• a special adjusting washer is installed under the drive gear (they are sold in sets, and the thickness of such washers varies from 2.5 to 3.7 mm);
• an adjusting sleeve is installed in the gearbox shank (these sleeves are also sold in sets, you can find them in any spare parts store);
• the washer and bushing must be selected so that the shaft on which the drive gear of the gearbox is installed rotates without play when scrolling it by hand. After the desired sleeve is selected, the nut on the shank is tightened;
  

  To adjust the gaps between the gears, wrenches with special indicators are usually used.
• when the shank is adjusted, the planetary gear is put in place (together with half of the gearbox housing). This half is held on by 4 bolts, and on the sides there are a couple of nuts for adjusting the differential bearings. The nuts are tightened in such a way that a slight play remains between the gears: the planetary gear must absolutely not be clamped too much;
• after adjusting the planetary gear, the position of the bearings in the differential should be adjusted. This is done with the same adjusting bolts, but now you have to use a feeler gauge to measure the gaps between the gears and the main shaft. The gaps should be within the range of 0.07 to 0.12 mm. After setting the required clearances, the adjusting bolts should be fixed with special plates so that the bolts do not turn away.
  

  After adjusting the gears with a feeler gauge, the clearance of the bearings and the shaft is adjusted

How to remove the rear axle gearbox VAZ 2107

The car owner can disassemble the gearbox and replace everything necessary in it (or change the gearbox entirely), thus saving about 1500 rubles (this service costs about XNUMX rubles in a car service). Here's what you need to work:

• a set of socket heads and a long collar;
• set of open-end wrenches;
• a set of spanners;
• puller for rear axle shafts;
• flat-blade screwdriver.

Sequence of work

Before starting work, oil must be drained from the rear gearbox. To do this, just unscrew the plug on the rear axle housing, after substituting some container under it.

1. The car is installed on the pit. The rear wheels are raised with jacks and removed. The front wheels must be securely locked.
2. After removing the wheels, unscrew all the nuts on the brake drums and remove their covers. Opens access to the brake pads.
   

   The bolts on the brake drum are unscrewed with an open-end wrench by 13
3. If you have a socket with a long knob, you can unscrew the nuts holding the axle shafts without removing the brake pads.
   

   After removing the drum cover, access to the pads and to the axle shaft opens
4. When all four nuts on the axle shaft are unscrewed, the axle shaft is removed using a puller.
   

   The rear axle shaft of the "seven" can be removed without removing the brake pads
5. After removing the axle shafts, the cardan is unscrewed. To unscrew it, you need an open-end wrench for 12. The cardan is held on by four bolts. After unscrewing them, the cardan simply moves aside, since it does not interfere with the removal of the gearbox.
   

   The cardan of the "seven" rests on four bolts for 12
6. With a 13 open-end wrench, all the bolts around the perimeter of the gearbox shank are unscrewed.
7. After unscrewing all the bolts, the gearbox is removed. To do this, simply pull the shank towards you.
   

   To remove the gearbox, you just need to pull it towards you by the shank
8. The old gearbox is replaced with a new one, after which the rear axle VAZ 2107 is reassembled.

Video: dismantling the rear axle on the "classic"

Dismantling the rear axle classic

Disassembly of the gearbox and replacement of satellites

Satellites are additional gears installed in the differential of the gearbox. Their purpose is to transmit torque to the axle shafts of the rear wheels. Like any other part, satellite gears are subject to wear. After that, they will have to be changed, since this part cannot be repaired. To restore worn teeth, the car owner does not have the necessary skills or the necessary equipment. In addition, any gear in a car undergoes a special heat treatment - carburizing, which is carried out in a nitrogen atmosphere and hardens the surface of the teeth to a certain depth, saturating this surface with carbon. An ordinary motorist in his garage will not be able to do anything like this. Therefore, there is only one way out: 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 a repair kit for gearboxes, you will also need a set of conventional open-end wrenches, a screwdriver and a hammer.

Sequence of operations

To disassemble the gearbox, it is best to use a conventional bench vise. Then the work will go much faster.

1. Removed from the machine, the gearbox is clamped in a vice in a vertical position.
2. A pair of adjusting locking bolts is unscrewed from it, under which the locking plates are located.
   

   Under the adjusting bolts there are plates that will also have to be removed.
3. Now the four bolts (two on each side of the gearbox) holding the bearing caps are unscrewed.
   

   The arrow indicates the bolt holding the bearing cover
4. Covers are removed. After them, the roller bearings themselves are removed. They must be carefully inspected for wear. At the slightest suspicion of wear, the bearings should be replaced.
5. After removing the bearings, you can remove the axis of the satellites and the satellites themselves, which are also carefully inspected for wear.
   

   Removed satellites must be carefully inspected for wear.
6. Now the drive shaft with bearing can be removed from the gearbox housing. The shaft is installed vertically, and is knocked out of the roller bearing with a hammer (in order not to damage the shaft, it is necessary to substitute something soft under the hammer, for example, a wooden mallet).
   

   In order not to damage the shaft, use a mallet when knocking out the bearing.
7. On this disassembly of the gearbox can be considered complete. All parts, including satellites and bearings, should be thoroughly washed in kerosene. Damaged satellites are replaced with satellites from the repair kit. If wear is also found on the gears of the axle shafts, they also change, along with the support washer. After that, the gearbox is reassembled and installed in its original place.

So, it is quite possible for an ordinary car owner to remove the gearbox from the rear axle of the “seven”, disassemble it and replace worn parts in it. There is nothing difficult in this. Certain difficulties can arise only at the stage of adjusting the new gearbox. But it is quite possible to cope with them by carefully reading the above recommendations.