One of the characteristic signs indicating the need to disassemble and adjust the gearbox is increased noise when the car is moving. Reasons for increased noise:
- - displacement of the contact patch in the engagement of bevel gears as a result of a violation of the adjustment of the conical bearings;
- - scoring and chipping of gear teeth, wear of bearings, as well as insufficient oil level in the axle housing.
Dismantling drive axles and their gearboxes
The procedure for dismantling the middle (rear) drive axle is as follows.
Mount the car on the inspection ditch. Close wheel valves (only for Ural-4320 and 4420).
Loosen the wheel nuts of the dismantled axle, remove the protective covers and disconnect the air supply hoses from the wheel valves.
Drain the lubricant from the axle housing.
Raise the rear of the vehicle and place a stand under the rear end of the frame. Loosen the wheel nuts and remove the wheels. Install and secure the fixture (Fig. 1).
Using the adjusting eccentrics, spread the brake pads, thereby preventing the axle beam from turning during subsequent disassembly operations.
Remove the cardan shaft of the drive of the middle (rear) axle, disconnect the brake hoses and pipelines, sealing systems (only for Ural-4320 and 4420), and tire inflation systems.
Disconnect the upper torque rod bracket from the bridge beam, disconnect and remove the lower torque rods.
Roll the assembly trolley under the bridge and, having removed the axle beam assembly, lower it onto the trolley using the tool.
Disconnect the device and roll out the trolley with the driving middle (rear) axle from under the car.
When removing the front axle, carry out preparatory work similar to those described above. Additionally, it is necessary to disconnect the steering bipod linkage from the left steering knuckle lever, the hydraulic booster from the right steering knuckle lever.
Disconnect and remove the lower shock absorber heads from the brackets.
Using the installed and fixed device, raise the axle and, having unscrewed the nuts of the stepladders, remove the clamps of the front springs.
Lower the front drive axle onto the cart.
Removing gearboxes from the vehicle
Set the dismantled front axle on stands. Disconnect the steering link rod, brake hoses and sealing systems.
Unscrew the ball joint nuts.
Using a spudger, remove the steering knuckle assemblies using the undercuts of the ball joint flanges.
Remove the side cover 35 (see Fig. 2) of the gear housing assembly with the oil supply fitting 25 and unscrew the bolts and nuts securing the gear housing, including two bolts located inside the housing.
Using a lifting mechanism, remove the gearbox from the axle housing.
Dismantle the gearbox of the middle (rear) axle using a device directly from the vehicle installed on the inspection ditch, to do this, close the wheel valves, remove the protective covers and disconnect the air supply hoses from the wheel valves.
Drain the lubricant from the axle housing.
Unscrew the bolts securing the hub caps, unscrew the air supply elbows from the axle shafts and remove the hub caps together with seals and air supply hoses. Then, using a puller, remove the axle shafts.
Remove the driveshaft of the middle (rear) axle drive. Disconnect and move aside the bracket of the upper torque rod together with the rod, pipelines and hoses of the brake system and the sealing system,
Remove the gearbox side cover assembly with the oil supply fitting, unscrew the bolts and nuts securing the gearbox crankcase, including two bolts located inside the crankcase.
Install the tool and remove the gearbox from the axle housing (Fig. 3).
The article describes the disassembly of the middle axle gearbox. Dismantling the gearbox of the front and rear axles about is carried out in a similar way.
Bend locking plates 23 (see Fig. 2) and lock washers 31, unscrew bolts 28 and 22.
Remove the 29 differential bearing caps.
It should be borne in mind that the holes in the gearbox housing for the differential bearings are processed together with the covers, and before disassembling the cover and the crankcase support on which they are installed, mark them with a core or paint, thereby preventing the depersonalization of the covers.
Remove adjusting nuts 32 and outer bearing races 33.
Remove differential assembly 30.
Unpin and unscrew the nut securing the flange 16 of the drive bevel gear shaft, locking the shaft from rotation.
Remove the flange using a puller.
Unscrew the bolts securing the cover 15 and remove the cover assembly with the sealing collar.
Unscrew the bolts securing the bearing cup and remove the shaft assembly with the bearing cup, the drive bevel gear, the shim pack 11 and the rear bearing inner ring 18 from the gearbox housing.
Remove the package of shims 11 from the cup of bearings. Unscrew the sealing plug 13 of the bridge.
Unscrew the bolts securing the cover 9 of the cup of the bearings of the cylindrical drive gear and remove the cover together with the package of shims 6.
Unpin and unscrew the bolts securing the pressure washer 10, remove the washer.
Using a puller or two cover fastening bolts 9, press out cup 5 together with tapered bearings 8 and a package of shims 4, using special threaded holes in the cup flange.
Fix the shim packs on the cover 9 and the cup 5 of the bearings. Through the side window, remove the driven bevel gear assembly from the gearbox housing.
If necessary, press out the outer ring of the bearing 2 (Fig. 4), the outer ring of the bearing 18 (see Fig. 2) complete with rollers from the seats of the gearbox housing and remove the oil supply fitting 25 from the hole in the side cover of the gearbox.
Disassembly of the driven bevel gear assembly
Place the bevel gear on stands and press out the drive spur gear shaft. Remove the support washer from it, remove the key from the groove of the shaft.
Install the driven bevel gear assembly with the inner race of the bearing on the stands and using the mandrel and three rods installed in the holes of the gear, remove the inner race of the bearings with rollers.
If necessary, use a mandrel to press the tapered bearings out of the cup.
Disassembly of the drive bevel gear shaft assembly. Secure the pinion shaft assembly in a vise.
Unpin and unscrew the nut 1 of the flange 2 (Fig. 5), remove the flange using a puller.
Unscrew the bolts securing the cover of 4 front bearings, remove the cover assembly with the sealing collar.
Bend the washer 14 and unscrew the lock nut 15. Remove the folding 14 and lock 13 washers and unscrew the nut 12.
Place the pinion shaft assembly on stands and press out the shaft.
Install the bearing cup assembly with the drive gear on the stands and with light blows of the copper hammer on the end, press the bevel gear out of the cup together with the bearing inner ring 11 and the adjusting washer 7.
Remove from the glass the inner ring of the bearing b complete with rollers. Remove the shim from the drive bevel gear shaft.
Using a puller, remove the bearing inner race 11 complete with rollers.
If there are scuffs or significant wear on the outer rings of bearings 6 and 11, press the rings out of the cup (3 - cuff).
If necessary, use a mandrel to press the sealing collars out of the bearing caps of the drive bevel gear shaft, remove the inner ring 10 of the bearing from the rear neck of the shaft.
Install the differential in a vise, clamping the rim of the driven spur gear 6 (Fig. 6).
If it is necessary to replace bearings 2, remove them with a puller.
Mark with a core or paint the relative position of the cups of the 3rd differential (the holes for the differential cross are processed as an assembly, and when disassembling, it is necessary to maintain the relative position of the cups).
Unpin and unscrew the nuts of the bolts 5 securing the differential cups, remove the bolts.
Install the differential on the fixture plate (fig. 7).
Insert a mounting blade into the spline hole of the side gear of the differential and use it to lift the end face of the driven spur gear above the plate.
Sharp hammer blows on the end face of the gear rim of the gear to press out the differential cup.
Remove pinion 1 of the axle shaft (see Fig. 6) with support washer 4.
Remove crosspiece 7 complete with satellites 9 (10 - satellite bushing) and supporting spherical washers 8.
Remove the axle gear with support washer from the second differential cup.
Press out the second differential cup.
Checking the technical condition
External inspection to check the condition of the body parts of the bridges.
It is not allowed to operate the car with the following defects:
- - cracks on the crankcase of the bridge and casings of the axle shafts; deflection of the bridge beam more than 4 mm;
- - wear and tear of the thread in the holes for the drain and filler plugs, in the holes for the bolts and studs of the gearbox.
To check the deflection (Fig. 8), install the axle beam on the prisms with the journals of the axle shaft casings under the outer hub bearings. Ensure that the plane of the bridge housing connector and the plane of the control plate are parallel. With an accuracy of 0.5 mm, determine the dimensions "B" and "C" and calculate the amount of deflection "H" of the bridge beam using the formula:
H = (B - 60) - (C - 71.25), where "B" is the actual size from the plane of the control plate to the upper part of the neck-casing of the axle shaft; C is the actual dimension from the plane of the control plate to the plane of the axle housing split in the middle part.
A bridge beam with a deflection of more than 4 mm should be edited. The bridge beam straightening scheme is shown in fig. 9.
When inspecting the parts of the gearbox, it should be borne in mind that the gears of the main gear and differential are not allowed to have cracks and chips in the middle part of the tooth, pitting on an area of more than 25% of the tooth surface.
Gears with chipped tooth tips at a length of not more than 5 mm from the end of the tooth, after cleaning the chips, are allowed for further work.
When rejecting a drive spur gear or one of the gears of a bevel gear pair of the final drive, it should be borne in mind that according to the manufacturing technology, these three gears are selected in a set and must be replaced as a set.
It is allowed to replace the drive spur gear or bevel gear pair with a mandatory check of the size of the neck of the driven bevel gear for bearing 2 (see Fig. 10) after it is pressed onto the shaft of the drive spur gear.
The diameter of the neck under the bearing after pressing the driven bevel gear should be within 90.012 - - 90.035 mm.
The runout relative to the axis of the driving spur gear is no more than 0.05 mm.
Differential cups are also included. If one of the cups needs to be replaced, they should also be replaced as a set.
Bearings with chips, cracks, destruction of separators, as well as chipping, shells, deep risks and brinelling on the raceways of the rings and rollers should be discarded.
The sealing collars of the axle shafts of the front drive axle and the bearing caps of the gearbox should be replaced if the working edges are torn, worn, hardened and cracked.
It is not allowed to loosen the fit of the seals in the cages and bearing caps. When replacing the sealing cuff of the front axle axle shaft, lock the cuff body after pressing it into the hole in the axle shaft housing by punching at two points.
On the parts of the hinges of equal angular velocities (forks, fists and disks), run-in (smoothed) scuffs are allowed, which are the result of the mutual running-in of new parts during the break-in period.
Step wear is not allowed on discs and knuckles. Data for the control of the details of the drive axles are given in table. 30, 31.
Reducer assembly and adjustment
Before the general assembly of the gearbox, assemble the components, lubricate with sealing lubricant, the threaded surface of the sealing plug, the mating surfaces of the covers and the gearbox housing.
Before installation, lubricate the bearings with gear oil, and the working edges of the sealing collars with TsIATIM-201 lubricant.
Assembly and installation of the driven bevel gear assembly
Using a mandrel, press onto the neck of the driven conicalth gear 1 inner race bearing 2 complete with rollers.
Into the groove of the shaft of the driving spur gear 5, press the key 3, install the support washer 4 on the shaft and press the driven bevel gear assembly with the inner ring of the bearing 2.
In case of rejection and replacement of one of the gears, assemble the driven bevel gear assembly in the following order.
Press the driven bevel gear 1 onto the gear shaft 5, check the size and runout of the bearing journal 2.
The diameter of the neck after pressing should be within 90.012 - 90.035 mm, and the runout relative to the axis of the driving spur gear should not exceed 0.05 mm. If necessary, grind the neck.
After machining the neck, press out gear 5 and assemble the driven bevel gear assembly in the order described above.
Install the gearbox housing and fix it in the fixture.
Press the bearing outer race 2 into the gearbox housing if it was pressed out during disassembly. Using a mandrel, press the tapered bearings 8 (see Fig. 2) into the cup 5 and install the cup with a package of shims 1 into the hole in the gearbox housing. Install and fix the cover 9 of the bearing cup with two bolts.
Install the sub-assembly of the driven bevel gear through the side window of the gearbox housing.
Unscrew the two cover screws 9 and remove the cover. Install and secure the clamping washer 10. Cotter the clamping washer fastening bolts with wire.
Install and secure the cover 9 of the cup of bearings with the sealing gasket 7 and the package of shims 6.
Check and, if necessary, adjust the bearing preload 8 by selecting the thickness of the shim pack 6.
The amount of torque required for smooth rotation of the driven bevel gear assembly should be in the range of 0.09 - 0.15 kgf / m, which corresponds to a force of 1.75 - 2.93 kgf applied to the drive spur gear.
When checking the adjustment of the bearing preload, local seizing is allowed up to 0.4 kgf.m.
Measure the torque value with continuous smooth rotation of the driven bevel gear assembly no earlier than after five full revolutions.
Assembly and installation of the drive bevel gear shaft
Before assembling the unit, determine the required thickness of the adjusting washer 7 (see Fig. 5). To do this, with an accuracy of ± 0.05 mm, determine the thickness of the shoulder of the cup 5 (dimension a - Fig. 10) and the distance between the ends of the inner and outer rings of the cup bearings (dimensions b and c). Determine the required thickness of the shim using the formula
S= (a + b + c) - 0.05, where a is the cup bead thickness; b is the actual size from the end of the inner ring of the front cup bearing to the end of the outer ring; c - the actual size from the end of the inner ring of the rear bearing of the glass to the end of the outer ring.
Having determined the size S, select the shim of the appropriate thickness.
At the factory, the preload of the tapered bearings of the assembly is adjusted by selecting the shim of the required thickness.
A set of factory-produced shims consists of 29 pcs. thickness 14.00; 14.05; 14.10;...; 15.40 mm.
If there is no set of shims and it is necessary to reduce the thickness of the existing shim, it can be ground.
Using mandrels, press the outer races of bearings 6 and 11 into the cup 5 (see Fig. 5) until it stops against the shoulder of the cup. Press the bearing inner race 11 complete with rollers onto the journal of the drive bevel gear 8.
Press the gear 8 onto the shaft 9 and fix the sub-assembled assembly in a vise, as shown in fig. 11.
On the neck of the driving bevel gear, install the adjusting washer 7 (see Fig. 5); at the same time, the wider end of the washer should be facing the gear ring gear.
Install the bearing cup 5 and, using a mandrel, press the inner ring of the bearing 6 complete with the rollers onto the gear shaft neck until it stops against the adjusting washer.
Screw nut 12 onto the gear shaft and tighten it.
The tightening torque of the nut should be within 45-50 kgf / m.
Tap several times with a copper drift and rotate the bearing cup so that their rollers are in the correct position.
Measure the amount of torque required to smoothly rotate the bearing cup of the drive bevel gear. The torque value should be in the range of 0.06-0.14 kgf / m, which corresponds to a force of 0.75 - 1.75 kgf, applied to the glass of bearings.
Measure the torque value with continuous smooth rotation of the bearing cup no earlier than after five full revolutions.
If, when measuring the torque value, the force of turning the glass is less than 0.75 kgf or more than 1.75 kgf, select an adjusting washer, the thickness of which is respectively less or more than 0.05 mm.
Having finished adjusting the bearings, install the lock 13 and 14 folding washers. If, when installing the lock washer, the pin of the nut 12 does not fall into the hole of the lock washer, tighten the nut (loosening the nut is not allowed).
If it is not possible to tighten the nut, it is allowed to cut the hole in the washer until it coincides with the pin of the nut. Tighten the lock nut 15 and lock it with a folding washer 14. The tightening torque of the lock nut should be 45 - 50 kgf/m.
On the neck of the rear end of the drive bevel gear shaft, install the inner ring of the bearing 10.
Install the assembled and adjusted unit with a package of shims 11 (see Fig. 2) into the gearbox housing. Bolt the cup of the drive bevel gear.
Using a mandrel, press the outer ring of the bearing 18 as an assembly until the rollers stop against the shoulder of the inner bearing ring.
Further, adjust the gear contact patch in the article "Adjusting the axle gearbox of the Ural car".
After completing the adjustment, install the bearing caps with gaskets and secure them with bolts.
Using a mandrel, press the flanges onto the splined ends of the drive bevel gear shaft, tighten and cotter the flange fastening nuts.
The cotter pin installed in the hole of the rear end of the drive bevel gear shaft must be located in the direction of the straight edge of the flange (i.e. when installing the flange, it is necessary to orient it relative to the shaft hole for the cotter pin).
The orientation of the flange on the shaft is provided to prevent contact between the cotter pin and the yoke of the cardan shaft being installed.
Assembling and installing the differential
Before assembling, lubricate the mating surfaces of the side gears, satellites and differential cross with gear oil.
If during disassembly of the differential, the inner rings of the bearings 2 were removed (see Fig. 6), install both cups 3 of the differential on the plate and, using a mandrel, press the bearing rings together with the rollers until they stop against the ends of the cups.
Place one of the differential cups on the stand. Install the driven spur gear 6 on the differential cup, aligning the holes in the cup and gear for mounting bolts 5.
Install support washer 4 and pinion 1 of the axle shaft into the differential cup. Install four satellites 9 with support spherical washers 8 on the spikes of the cross 7. Place the cross together with the satellites in the sockets of the differential cup.
Place the second gear of the axle shaft with the support washer on the pinion gears. Position the support washer on the neck of the side gear in such a way that after installing the second differential cup, the mustache of the washer falls into the lubrication holes of the cup.
Install the second differential cup, matching the marks made during disassembly.
Insert bolts 5 into the holes of the differential cups and the hub of the driven spur gear, screw the nuts onto the bolts. Install the bolts from the side of the larger recess of the gear hub.
Install the differential in a vise while clamping the rim of the driven spur gear. Tighten the nuts of the differential cup bolts.
Check the correct assembly of the differential. The rotation of the gears in the assembled differential must be free when turning the gear of the axle shaft with a splined mandrel.
After finishing the check, cotter the nuts of the differential cup bolts.
Install the assembled differential on the gearbox housing supports; in this case, the crown of the driven spur gear should take a position symmetrical with respect to the crown of the driving spur gear, and the heads of the bolts for fastening the differential cups should be directed towards the driven bevel gear.
Install the bearing outer races and position the differential bearing caps according to the marks made during disassembly. Tighten the cover bolts. Bolt tightening torque 25 kgf/m.
Tighten the adjusting nuts until the ends of the nuts and the outer rings of the bearings touch.
Adjust differential bearings. to do this, install an indicator bracket and, turning one of the adjusting nuts, increase the distance between the differential bearing caps by 0.15 - 0.25 mm. At the same time, for the correct installation of the bearing rollers, rotate the differential several times by the driven spur gear.
After completing the adjustment, install the locking plates into the grooves of the adjusting nuts 27 (see fig. 2) and fix them with bolts 28.
Lock the corresponding bolts by bending the locking plates 23 and lock washers 31. Screw the bridge sealing plug into the hole in the gearbox housing.
Check the operation of the assembled gearbox by rotating by hand on the flange of the drive gear shaft. In this case, the gears should rotate without noticeable jamming.
Run the assembled drive axle gearbox on a special stand, and in the absence of a stand, test it with a control run on the car.
Reducer on the stand to test with reversing and braking at a speed of the drive bevel gear shaft of 1000 rpm.
To avoid scuffing and seizing, the duration of the test should not exceed 0.5 minutes.
Evidence of proper assembly and adjustment of the gearbox is the absence of knocks, increased gear noise and the presence of a contact patch on both sides of the tooth of the driven bevel gear.
If there is increased noise or knocks, disassemble the gearbox. Check the adjustment of the bearings, the position of the contact patch and, if necessary, repeat the adjustment of the gearbox.
Testing drive axles. After assembly, run the drive axle on the stand without load.
Run in at a speed of 1200 - 1500 forward and reverse for one minute. And at a speed of 2400 - 2600 forward 3 minutes.
Before testing, pour 4 liters of I-20A industrial oil into the axle housing. During the break-in, check the smoothness and noise of the gearbox, as well as the operation of the front axle hinges by turning the hubs in both directions.
After running in, drain the oil from the axle housing.
Check the drive axles of the Ural-4320, -4420 vehicles for tightness of the air supply cuffs, as well as the connections of the gearbox, axle beam and steering knuckle assemblies.
Check the air supply cuff for leaks for 10 minutes under an air pressure of 3.2 kgf/cm2.
The threaded holes of the axle shaft housings (or fittings of the front axle pivot pins) for the tips of the flexible hoses of the tire inflation system are to be plugged.
Supply air through the air supply hoses.
Air leakage during testing is not allowed.
Check the tightness of the connections of the middle (rear) drive axle by supplying air through the hole in the gearbox housing under the plug of the sealing system.
When testing the front drive axle, check the tightness of the joints of the gearbox and the steering knuckle assemblies, while simultaneously supplying air through the holes in the housings of the steering knuckles and the gearbox housing under the fittings and the plug of the sealing system.
Air pressure during testing 0.35 kgf/cm2, allowable air pressure drop is not more than 0.1 kgf/cm2 for 1 min.
During the test, make several revolutions of the drive bevel gear shaft, and also turn both housings of the front axle steering knuckles from one extreme position to another.
Install the gearbox (bridge) on the car in the reverse order of dismantling. After tightening the bolts and nuts securing the gearbox housing, cotter the two bolts located inside the housing with wire.
When installing the side cover of the gearbox housing, cover both sides of the sealing gasket 34 (see Fig. 2) with a thin layer of oil paint.
Having fixed the side cover of the front axle gearbox housing, lock the two screws securing the cover by punching at two points.