Do-it-yourself gearbox repair in the field

In detail: do-it-yourself repair of a gearbox in a field from a real master for the site my.housecope.com.

We will show you how to quickly remove the rear axle gearbox in NIVA with your own hands (VAZ 2131, VAZ 2121). On this machine, the gearbox has worn out and has become unusable, it needs to be replaced. We start by unscrewing the wheels. Unscrew the bottom of the oil drain plug with a 12 hexagon:

We drain the oil. We unscrew the propeller shaft, 4 nuts on a turnkey basis by 13, unscrew the nuts, take out the bolts, move the propeller shaft forward and remove it:

We begin to unscrew the brake drums, here the thread is 8, there you can tighten the bolts and push the drum away from the axle shaft, if it is difficult to remove it with your hands:

We unscrew the "brake mechanism", behind 4 nuts with a 17 wrench:

Bolts with grinded caps, they will not scroll, so the nuts can be safely turned, although it will be inconvenient to put on a spanner wrench.

We pulled the brake shield to the spring with a coupler so as not to remove the brake pipe, after that we pull out the axle shaft:

An oil seal was found inside that was leaking, we will replace it. The gearbox itself is fastened with 8 bolts under the head by 12, we unscrew them, it also sits on the sealant, with the help of a screwdriver we “knock it down” a little. The gearbox is removed, you can repair it or install a new one.

Video removal of the rear axle gearbox in the NIVA car:

Backup video how to remove the rear axle gearbox on NIV:

Adjusting the front axle of the niva is one of the key operations that ensures comfortable and trouble-free travel on roads of any quality.

The need to adjust the elements of the front axle is assessed by the presence of noise and vibrations that occur in various operating modes of the VAZ 21214. So, conditionally acoustic signs can be divided into two groups:
• Registered constantly;
• Fixed when braking with internal combustion engine or acceleration.

Video (click to play).

By nature, sounds can resemble:
• Howl (wear of the main pair);
• Crunch, "trolleybus" hum (destruction or hauling of the shank bearings, loose nut of the drive shaft, axle shaft bearings, incorrect adjustment of the gears of the main gearbox);
• Intermittent "scuffing" (differential bearing).
The complexity of diagnostics in this case lies in the abundance of extraneous noise emitted by other parts of the car.

To carry out adjustment work on the front axle, the manufacturer provides special pullers, mandrels and devices. However, due to their limited distribution and high cost, their presence is not necessary, although it is desirable to save time and accuracy of tuning.
Since the main parts of the RPM correspond to similar elements of the REM, the correspondence of the technological clearances and the procedure for carrying out repair operations is traced.

The main stage is preceded by preparation, including:
1. Drain the oil from the RPM through the drain hole;

2. Disconnecting the propeller shaft with a key 13

3. Removing the right wheel drive.

4. Dismantling the lower ball joint on the left side.

5. Removal of suspension braces.

6. Removing the gearbox from the brackets on the right and left using the stop.

This is followed by disassembly of the gearbox, thorough cleaning of surfaces from dirt and grease, and troubleshooting of components.

To carry out the operation, the original device A.95690, mandrel A.70184 or an analogue made according to the drawing are used.

The seating plane of the crankcase is positioned so that it takes a horizontal position. Then an absolutely flat metal bar is installed on the bearing bed.The distance from the bar to the mandrel is measured by inserting adjusting rings from a set in 0.05 increments into the gap under the bar. The measured value (base of the crankcase) is consistent with the correction applied to the pinion.
When reassembling the assembly, it is recommended that the standard spacer be discarded to prevent re-repair. Instead, a non-deformable steel sleeve with a length of 48 mm is suitable (with a margin, if necessary, shorten it).

During turning, the parts control the force when turning the gear (should be 157-196 N · cm), for bearings with mileage, a torque of 39.2–58.8 N · cm is valid. The use of a proprietary dynamometer 02.7812.9501 is optional.

Acceptable accuracy will be provided by a household steelyard. When working with it, wind one end of a 1 m long cord around the flange, and fasten the other to the balance. Lock the torque by pulling the device in a perpendicular direction. So, new bearings should provide 7-9 kg, and with mileage - 2-3 kg.

The process involves replacing the support washers with new ones - thicker than before. A choice of 7 standard sizes with a step of 0.05 mm in the range of 1.8-2.1 mm. Washers material - bronze or steel. In this case, the gears are installed tightly, but with the ability to turn manually.

In accordance with the instructions, the lateral clearance and bearing preload are adjusted using the A.95688 / R tool.

In its absence, a vernier caliper of a suitable size will perform the given role.

To ensure the required preload, the distance relative to the bearing caps is recorded at the beginning of the tightening and at the end of it. The required difference between the values is 0.2 mm.

The lateral clearance is adjusted by bringing the driven gear to the leading one until it disappears. Initially, one of the nuts is in a free position, the other (working) is tightened. After eliminating the gap, gradually tighten the baited nut until the jaws of the caliper move apart by 0.1 mm.
The backlash adjustment stops when a slight knock of the teeth appears. Then both nuts are evenly tightened to a distance of 0.2 mm. The correctness of the work performed is evidenced by a uniform backlash at any position of the gears.

We remove the gearbox to replace it, repair or replace the rear axle beam.
We hang out the rear axle.We drain the oil from the rear axle housing (see here).Disconnect the rear propeller shaft from the rear axle reducer flange (see here).Holding the gearbox housing, use the "12" head to unscrew the eight bolts of its attachment to the rear axle beam.... and a gasket.
Install the gearbox in reverse order.
Before installing the gearbox, we clean the mating plane of the beam. Install a new gasket. Before tightening the bolts securing the gearbox to the rear axle beam, apply sealant to the bolt threads.Before removing, we clean the gearbox from dirt. We install the dismantled gearbox on the workbench.Using the "10" wrench, unscrew the bolt securing the locking plate of the adjusting nut of the right bearing of the differential box ...Similarly, remove the retaining plate of the left bearing adjusting nut.Using a punch, we mark the location of the differential box bearing caps on the gearbox housing.With a spanner wrench "17" we unscrew the two bolts securing the cover of the right bearing of the differential box ...Remove the right bearing cover.We take out the adjusting nut ...... and remove the outer bearing race of the differential box.Likewise, remove the cover, take out the adjusting nut and remove the outer ring of the left bearing of the differential box.If we do not change the bearings of the differential box, then we mark their outer rings in order not to confuse them during assembly.We remove the differential box assembly with the driven gear of the main drive, inner rings, cages and bearing rollers.We take out the drive gear assembly from the gearbox housing with an adjusting ring, an inner ring, a cage and rear bearing rollers and a spacer sleeve.Striking blows with a hammer through a drift on the inner ring of the rear gearbox bearing, ...… Remove the inner ring with cage and rollers.Remove the drive gear adjusting ring.We remove the oil seal from the housing of the gearbox (see here).... and the inner ring of the front bearing with cage and rollers.With a punch we knock out the outer ring of the front bearing of the drive gear ...Turning the crankcase over, knock out the outer ring of the rear bearing of the drive gear in the same way.For disassembling the differential…... with a puller we press the inner ring of the differential box bearing.In the absence of a puller, insert a chisel between the end of the bearing inner ring and the differential box.

By striking the chisel, we move the inner ring of the bearing.We insert two powerful screwdrivers (or mounting blades) into the formed gap and press it ...… Inner ring with cage and rollers.Similarly, we press the inner ring of the other bearing.Clamping the differential box in a vice with soft metal jaw pads, ...... with a 17-ring spanner, unscrew the eight bolts securing the driven gear to the differential box.Using a hammer with a plastic striker, we knock down the driven gear from the differential box ...Turning the satellites, take them out of the differential box.We take out the side gears.Before assembly, we wash the gearbox parts in kerosene and inspect them. We check the condition of the teeth of the main gears. Damage to at least one tooth (chipping, scuffing of the working surface) is unacceptable. With a fine-grained sandpaper, we eliminate minor damage to the pinion axle, the axle pinion journals and their mounting holes in the differential box. In case of serious damage to the parts, we replace them with new ones. If even minor damage to the surfaces of the bearing washers of the semi-axle gears is found, we replace the washers with new ones (with a selection of the thickness of the washers). Bearings of the pinion gear and differential box must be free of wear, with smooth working surfaces. Poor bearing condition causes noise and seized gear teeth.The inner rings of the differential box bearings with cages and rollers are pressed onto the box with a suitable piece of pipe. We fix the driven gear on the differential box.When assembling the differential, we lubricate the semi-axle gears with support washers and satellites with transmission oil and install them in the differential box. We turn the satellites and the gears of the semi-axles so as to align the axis of rotation of the satellites with the axis of the holes in the differential box, and insert the axis of the satellites. The axial clearance of each half-shaft gear must not exceed 0.1 mm. With an increased clearance, we replace the bearing washers of the semiaxis gears with new ones - of greater thickness. The moment of resistance to the rotation of the differential gears should not exceed 14.7 N.m (1.5 kgf.m) - the gears are turned by hand.We check the ease of rotation of the differential gears.Press the outer ring of the front bearing into the housing with a tool head of a suitable diameter (a piece of pipe).Similarly, we press in the outer ring of the rear bearing.The correct position of the drive gear relative to the driven gear is ensured by the selection of the thickness of the adjusting ring installed between the end face of the drive gear and the inner ring of the rear bearing. When replacing the main pair of the gearbox or the bearings of the drive gear, we select the adjusting ring.To do this, we make a device from an old drive gear: we weld a plate 80 mm long to the gear and grind the plate to a size of 50–0.02 mm relative to the end of the gear (the adjoining plane of the adjusting ring).A device made from an old pinion gear.We grind (or process with fine sandpaper) the place where the rear bearing is installed on the drive gear so that the inner ring of the bearing is installed on a sliding fit. On the manufactured device, we install the inner ring of the rear bearing with a cage and rollers and insert the device into the crankcase. Then we install the inner ring of the front bearing with a cage and rollers and the flange of the drive gear. Turning the gear wheel for the correct installation of the bearing rollers by the flange, tighten the flange mounting nut to a torque of 7.9–9.8 Nm (0.8–1.0 kgf.m).We fix the crankcase on the workbench so that its attachment plane is horizontal. We install a curved ruler in the bearing bed with an edge so that the bed ruler touches along the line.Using a set of flat probes, we determine the size of the gap between the ruler and the fixture plate.The thickness of the adjusting ring is determined by the difference between the gap and the deviation from the nominal position of the new gear (taking into account the sign of the deviation).The marking of the deviation from the nominal position (in hundredths of a millimeter with "plus" or "minus" signs) is applied to the tapered part of the gear shank.For example, the measured clearance is 2.90 mm and the gear has a -15 deviation from the nominal position. We translate the deviation into millimeters: –15 x 0.01 = –0.15.The required shim thickness is: 2.90 - (- 0.15) = 3.05 mm.We install the adjusting ring of the required thickness on the new drive gear. We remove the device from the gearbox housing and remove the inner rings of the front and rear bearings with cages and rollers.With a suitable piece of pipe, press the inner ring of the rear bearing with a cage and rollers onto the new drive gear.We insert the drive gear into the gearbox housing. Install a new spacer sleeve, an inner ring of the front bearing with a cage and rollers, and an oil deflector. Having lubricated the working edge of the new oil seal with Litol-24 grease, we press it into the crankcase socket. Install the pinion flange.Having locked the flange, gradually tighten the nut of its fastening with a torque wrench to a moment of 118 Nm (12 kgfm).The preload of the drive pinion bearings is controlled with a dynamometer.… Periodically checking the bearing resistance torque to the rotation of the drive gear.If the moment of resistance to rotation turned out to be less than 157 Ncm (16 kgf.cm) - for new bearings, and for bearings after 30 km of run - less than 39.2 Ncm (4 kgf.cm), then tighten the flange mounting nut, do not exceeding the tightening torque. After that, we again check the moment of resistance to the rotation of the drive gear.If the moment of resistance turned out to be more than 197 Ncm (20 kgf.cm) - for new bearings, and for worn-in bearings - more than 59.0 Ncm (6 kgf.cm), then the preload of the bearings is exceeded.In this case, replace the overly deformed spacer with a new one and reassemble and re-adjust.We install the differential assembly with bearings and adjusting nuts in the gearbox housing so that they come into contact with the outer rings of the bearings. We tighten the bearing cap bolts to the required torque.We make a special wrench for tightening the adjusting nuts from a steel plate 49.5 mm wide and 3-4 mm thick.The adjustment of the lateral clearance in the meshing of the main drive gears and the preload of the differential box bearings are carried out simultaneously, in several stages.Using a vernier caliper, we measure the distance between the bearing caps.We wrap the left adjusting nut (from the side of the driven gear) until the gap in the meshing of the main gears is completely eliminated.We turn the right nut until it stops and tighten it by 1–2 teeth of the nut.Tightening the left nut, we set the required lateral clearance of 0.08–0.13 mm in the meshing of the main gears.With this gap, shaking the driven gear, with the fingers of our hand we feel the minimum backlash in the engagement of the gears, accompanied by a slight knock of the tooth against the tooth.
When the nuts are tightened, the bearing caps of the differential boxes diverge and the distance between them increases.To set the preload of the differential box bearings, successively and evenly tighten both bearing adjusting nuts until the distance between the covers is 0.15–0.20 mm. Having established the preload of the bearings, we finally check the lateral clearance in the meshing of the main gears, which should not change. For this,…... while slowly turning the driven gear three turns, use your fingers to control the backlash in the engagement of each pair of teeth.If the clearance in the engagement turns out to be greater than the required one (0.08-0.13 mm), then by rotating the adjusting nuts we bring the driven gear closer to the driving gear or move it back if the clearance is less. In order to maintain the established bearing preload, we move the driven gear by tightening one of the adjusting nuts and loosening the other by the same angle.After adjustment, install the locking plates of the adjusting nuts and fasten them with bolts.The VAZ Niva 2121 is the first domestic off-road vehicle, which has become a real convenient and comfortable SUV. There were just cars that could move off-road before, but it was excruciatingly inconvenient inside them, as an example, you can recall the same UAZ 469. The salon there is really spartan, and when you go through potholes, the risk of meeting the head and the ceiling is unusually high due to the design pendants. In addition, at that time only the military could have a UAZ, it was not available for sale. But Niva 2121 is a completely different movie.

This car received a completely new interior, in some places, of course, borrowed from other VAZ models. The suspension is soft here, it was possible to make it this way because there is no frame, but a supporting body. Both axles are leading here, the car received a four-speed gearbox and a fairly reliable transfer case. Due to the small trunk, I had to figure out where to put the spare wheel so as not to reduce the trunk space. We put it under the hood, constructing a stand under it so that it was placed on top and did not take up space.The VAZ Niva 2121 has all driving axles, since this is a full-fledged SUV, where each wheel rotates from the engine. However, the axles here still have differences: the rear axle is simply driven, and the front axle is driven and steered. Structurally, these two axles are united by the presence of a crankcase and the presence of a gearbox. They look almost the same here, but we are interested in the front axle gearbox.In general, each gearbox has an identical function: to receive torque. The torque generated by the engine is first absorbed by the clutch and gearbox.After it comes the transfer case, which distributes the torque to two propeller shafts, which abut against the gearbox. He also perceives the moment and turns it 90 degrees, rotating each axle shaft with a wheel. Image - Do-it-yourself gear repair in the field

Front gearbox VAZ Niva 2121

The gearbox of the VAZ Niva 2121 car consists of the following elements:

Pinion gear.
Driven gear.
Gears of each axle shaft.
Satellites.

If the gearbox starts to fail, then this is determined immediately by the sound. There is such an expression - “the bridge howls”.This worn out gear starts to engage poorly and creates a pulling sound when accelerating, which is similar to the howling of a dog.

Today, gearbox repair usually comes down to buying and installing a new one. Earlier, in our Soviet times, on a car rem. almost everything was repaired in factories, and the ground gear teeth were welded and restored. Today, no one does this, but simply replaces it. Nevertheless, you first need to troubleshoot the gears in order to determine whether the statement that the VAZ Niva 2121 gearbox is worn out and needs to be replaced is true. D

To remove the gearbox, we need to remove the entire auto bridge. Therefore, we must figure out how to disassemble and remove it from the car.

First, we need to decide on the place of repair - it must be a good comfortable pit or a high lift. The first step is to remove the engine protection as it covers most of the underbody in the front of the car. Then we unscrew and remove the bar at the anti-roll bar, and at the cross member we must remove the stretch marks. Our next step is to detach the shock absorbers from the lower suspension arms. Next, we unscrew the propeller shaft from the flange of the drive gear and carefully move it to the side, perhaps for this it will need to be turned. Do not be afraid if you manually crank the crankshaft, nothing bad will happen or break.Now we need to compress the suspension springs with a special device and immediately remove the ball joints from the lower arm. Smoothly releasing the spring clamps, we also remove them. You also need to remove the rods from the swing arms. Now you need to remove the cap and carefully unscrew the bearing nut. The same is done on the other side of the VAZ Niva 2121 suspension. Now you need to disconnect the muffler mount on the gearbox and in the rear of the engine and remove the muffler.Now we need to unscrew the nuts securing the cross member of the engine mountings. Remove the bolt that secures the right-hand bracket to the engine and the two nuts that secure the front axle. At the same time, it is desirable to maintain the bridge.Now that the VAZ Niva 2121 bridge has been removed, it needs to be fixed to the stand. Now we need to remove the cover and take out the hinge, it is just as important not to rip off the gasket. At the axle housing, you need to remove the stamped cover and another gasket. That's it, the gears of the reducer have opened in front of us, and we can take it out. In this case, do not remove the lower crankcase cover, because oil may leak out and pour over you. You also need to take out the gears carefully, since they weigh a lot.

There is a weak point in the design of the assembly - the spacer sleeve 20 (the so-called barrel). As conceived by the developers, it, deforming when tightening the nut 22, should maintain sufficient elasticity throughout the entire service life of the machine, providing a constant preload in the bearings of the drive gear. This solution greatly simplifies and reduces the cost of assembling gearboxes at the plant - there is no need to select the thickness of the shim package, as in the Volga and Muscovites bridges.

By the way, the first sign of the axial play of the drive gear is the appearance of oil on the throat of the gearbox. When the vehicle is moving forward, the gear loads the rear bearing and relieves the front bearing, trying to “wriggle out” from the engagement. In this case, in addition to the axial play, a radial appears in the front bearing and the oil seal on the flange 1 no longer retains oil.

If you often have to drive the car in reverse, and even under load, uphill - the agony of the “sick” unit will not last long. The fact is that in the reverse mode, the drive gear, choosing the axial play, is screwed into the driven gear, as it were, shifting backward, which, with the tapered shape of the gear rims, causes a huge lateral force in the bearings. In especially advanced cases, the backlash progresses like an avalanche and the gear "goes" back so far that it mills a deep furrow on the surface of the differential box. Of course, the cemented layer on the working surfaces of the teeth will be worn out by that time, the tops of the teeth are rounded and the hum of the rear axle will turn into a growl with an eerie crunch ...

How can you determine the suitability of certain parts for reuse in a newly assembled gearbox? The main couple, perhaps, will still serve - the final verdict will make her a noise test. Do not be alarmed: instead of an expensive stand with an electric drive, you can use an ordinary knob with a 24 ”head from a large set of socket tools, and the measuring acoustic complex will replace your own ears. The assembled gearbox (without a spacer sleeve, oil seal, oil deflector, differential parts and stoppers, but with an adjusted gap in the engagement of the pair) is fixed in a vice, placing cardboard under the jaws so as not to jam the flange. Then quickly rotate the drive gear by the flange nut. If, instead of a soft rustle of bearings, a rumble resonating into the workbench cover is heard, even more so a pulsating one - we throw out the main pair without a shadow of a doubt - no adjustment "by the contact patch" will save it.

You can also reject the main pair visually, for example, if the tape of the top of the drive gear tooth is not uniform in width, as in the new one, but is narrowed in the middle part. The edges between the tops and working surfaces of the driven gear teeth must be sharp, like a turning tool. If you see the slightest nicks or roundings, throw away the steam without hesitation. And, of course, the main pair must be replaced if chipping of the cemented layer, waves, risks and other defects are visible on at least one of the teeth.

The differential box must be replaced if its journals are squashed and the new bearings are easy to put on by hand. It is unacceptable to grind the necks under the repair bushings - they are already thin. Whenever the gearbox is repaired, the bearings should be replaced with new ones, even if the old ones look quite functional. The saturation of oil with metal wear particles does not pass without leaving a trace for them, so the savings are more expensive here.

There is no need for expensive, heavy-duty jaw pullers to press out the bearing rings - they are superbly replaced by two hardened, thin-tongued mounting blades - much faster than fitting a fixture.In addition, when pressing the bearing rings into the crankcase or onto the gear with a puller, the following drawback appears: tightening its screw to failure, you will not feel the full fit of the ring around the entire circumference without a gap. It is possible that when the unit is in operation, it will settle down a little more, loosening the bearing preload. In my experience, it is safer to press in rings with a hammer using mild steel pipe pieces as mandrels. The first blows will be "sticky" - the ring moves along the neck or in the bore, and then the hand will feel the sharp return of the hammer - that means that everything is "gap - zero". A few more light, “stroking” strokes around the circumference and you can be sure - the ring is set all the way.

To match it with the new main pair, we subtract from it the amount of the correction applied with an electrographic pencil in the middle part of the drive gear. The marking, made in sloppy, sweeping handwriting, includes four digits of the main pair number (it is also stamped on the driven gear) and one or two correction digits with a "+" or "-" sign, denoting hundredths of a millimeter. For example, the base of the crankcase is 2.65 mm, and the correction is "-7". Subtract: 2.65 - (–0.07) = 2.65 + 0.07 = 2.72. This means that a ring 2.70 or 2.75 mm thick must be placed under the rear bearing of the drive gear. If you do not have this, you can grind a thicker one, for example, in a lathe or, at worst, rubbing it on a plane with sandpaper.

When installing the drive gear in the crankcase, it makes sense to abandon the standard spacer sleeve - its elastic properties are unlikely to last for a long time, the preload in the bearings will weaken and, perhaps, after a year, the unit will have to be sorted out again. But nothing prevents us from installing a rigid, non-deformable bushing. That is exactly how, choosing the thickness of the package of adjusting gaskets between the rigid bushing and the bearing, the gearboxes were assembled in the "pre-Zhiguli" times - laboriously, but reliably! We order the sleeve to a turner, taking into account that the size of 48 mm is given with a margin - by gradually shortening the part (for example, with a file or on emery), we will set the required preload in the bearings.