The Ural-4320 and its modifications have a mechanical two-stage transfer case (Fig. 1) with an asymmetric center differential
During the operation of the car, the transfer case is periodically removed from the car in a planned manner to inspect and adjust the axial play of the input and intermediate shafts. It is advisable to eliminate the noticed malfunctions at the same time.
The design of the transfer case allows you to remove the input shaft with gears, the drive shafts of the front and rear axles from the crankcase without completely disassembling it.
The rear axle drive shaft can be removed as an assembly with the differential.
Faults such as leakage of lubricant, loosening of the flange nuts on the shafts can be eliminated without removing the transfer case from the vehicle.
Elimination of such malfunctions as arbitrary disengagement of gears (wear of the splines of the gear shift carriage and input shaft) or differential lock (wear of the splines of the differential lock clutch and the front axle drive shaft), breakdown, misfitting of parts, as well as adjustment work in the scope of the technical maintenance are performed on a transfer case removed from the car and partially disassembled.
The need for complete disassembly of the transfer case rarely appears and, as a rule, after a long operation of the car.
Lubricant leaks should be detected by inspection and eliminated by tightening plugs, bolts of bearing caps or replacing gaskets and cuffs.
Random disengagement and differential lock can be detected when the vehicle is driven with a variable load in severe road conditions. At the same time, the transfer case control levers move arbitrarily:
- - shift lever towards the neutral position;
- - differential lock lever in the direction of disengaging the lock.
With increased wear, scuffing and breakage of parts of the transfer case, the noise of operation changes, extraneous knocks may appear when the car is moving under normal road conditions.
Experienced drivers and mechanics usually detect these faults by ear.
Dismantling the transfer case
It is more convenient to remove the transfer case if the car is installed on an inspection ditch in a room equipped with a load-lifting device.
To dismantle the transfer case from Ural-4320, -4420 and -44202 vehicles, lower the hinged bracket of the spare wheel holder and remove the wheel.
Remove the cardan shaft of the middle axle drive, disconnect from the flanges of the transfer case and the additional power collection box the flanges of the cardan shafts of the intermediate, front axle drive and front winch drive.
Disconnect the wires from the speedometer sensor.
Unpin and remove the pins, disconnect the rear ends of the control rods for the transfer case, auxiliary power take-off and parking brake.
Unscrew the sealing tube from fitting 11.
Move the disconnected ends of the cardan shafts and control rods for the transfer case, auxiliary power take-off and parking brake to the side and fasten to the vehicle frame.
Mount the lifting device by the bracket on the cover 4 of the top hatch of the transfer box and slightly tighten the slings of the sling device.
Unpin and unscrew the nuts of the studs securing the transfer case to the brackets, remove the pillows and washers, carefully lower the box onto the trolley and remove it from under the car frame.
Disassembling the transfer case
First, disassemble the transfer case into large units, and then these units into separate parts.
It is more convenient to start a complete disassembly of the transfer case by disassembling the control mechanism. To do this, unpin and remove the fingers, disconnect the leads 14, 15 (Fig. 4) from the rods 17, 19.
Unlock and unscrew the nuts 13 that fasten the drivers to the bracket 16, remove the drivers and bushings 21 from the rollers 22.
Unscrew the plugs 19 (see Fig. ) and use a wire hook to remove the springs and balls from the housings 22 and 20 of the locking mechanisms gears and differential lock.
Unscrew the bolts, remove the bracket 16 (see Fig. 2) and housings 18 and 20 of the fixing mechanisms.
To remove the input shaft 7 from the crankcase (see Fig. 1), unscrew the bolts and remove the cover 4 with the gasket, the lifting bracket.
Storage the input shaft through the top hatch. Unpin and unscrew the front flange fastening nut, remove the washer and press the flange with a universal puller.
Remove the bolts and remove the front and rear input shaft bearing caps.
Remove sealing and adjusting 30 gaskets and fix them on the corresponding covers.
On Ural-4320 vehicles equipped with a winch, remove the additional power take-off box installed in place of the rear bearing cover.
Insert a soft metal spacer between the top gear 3 and the back wall of the crankcase 6.
In place of the front bearing cover, install a puller and press the input shaft assembly out of the crankcase (Fig. 3).
Remove top gear 3 (see fig. 1) with bushing, support washer 2, front bearing inner race 1, soft metal spacer and gear shift carriage 5 through the upper crankcase hatch.
Using a puller, press out the front bearing outer race 1. Release the parking brake.
To remove the intermediate shaft 29 and gears 16 and 28 (see Fig. 1), unscrew the bolts, remove the front and rear bearing caps, adjusting 9 and gaskets.
Attach the gaskets to the appropriate covers.
Unscrew the nut 12 of the rear bearing 14, remove the thrust washer 13.
In place of the rear cover, install a puller and press the intermediate shaft assembly out of the crankcase (Fig. 4).
Through the top hatch, remove the gears 28 and 16 (see Fig. 1) of the higher and lower gears, the spacer sleeve 15, the rear bearing inner ring and the gear selector fork assembly with the stem 23.
Install the puller and press out the rear bearing outer race.
To remove the shaft 27 of the front axle drive unscrew the bolts securing the bearing cover and, shaking with light hammer blows on the flange, remove the shaft assembly (Fig. 5).
Remove the gasket and attach it to the lid.
To remove the shaft 24 (see Fig. 1) of the rear axle drive, unscrew the bolts securing the rear bearing cover.
Separate the cover from the crankcase with light hammer blows.
In the gap formed between the crankcase and the cover, carefully, so as not to damage the gasket, insert two screwdrivers.
Remove the shaft by rocking it (Fig. 6).
Remove the gasket and attach it to the lid.
To remove the differential unscrew the bolts securing the differential rear bearing housing.
Separate the rear bearing housing from the transfer box housing with light blows and secure it to the load handler hook.
Remove differential assembly from crankcase. Unscrew the stem 21 (see Fig. 1) and remove the fork 18 together with the clutch 26 of the differential lock.
Remove the gasket and attach it to the rear bearing housing.
When completely disassembling the units, install the input shaft 2 (see Fig. 3) by the splined part in a vice.
Unscrew nut 8, remove lock washer 7.
Using a universal puller, press low gear 4 with bushing 3, support washers 5 and rear bearing inner ring 6 (1 - bushing).
Install the intermediate shaft 9 (see Fig. 4) by the splined part in a vise, bend the antennae of the locking plate 2 and unscrew the bolts 3 fastening the gear 1 of the speedometer drive.
Remove lock plate 2, thrust washer 4, gear 1 and key 5.
Unscrew the nut 6 of the bearing fastening, remove the support washer 7 with a universal puller, press the inner race of the bearing 8.
Install the front axle drive shaft (see Fig. 5) in a vise by the splined part.
Remove cotter pin 2 and unscrew nut 1, remove washer 3 and press flange 4 with a puller.
With light blows on cover 8, press it off bearing 10, remove oil ring 6 and thrust washer 7.
Remove the retaining ring 9 from the bearing and press the bearing off the shaft 12 with a puller, remove the thrust washer 11 (5 - cuff).
Disassemble the rear axle drive shaft in the same way as the front axle drive shaft was disassembled, after removing the retaining ring 7 (see Fig. 6).
When disassembling the differential (Fig. 8), bend the ends of the locking plates 21 and unscrew the nuts 8 of the studs securing the front cage 1 to the gear of the lower shaft 9.
Remove the locking plates with light strokes and separate the front race assembly with washer 20, satellites 5 and sun gear 17 from the gear of the lower shaft. Remove the main gear 16 from the rear race 11.
Place the front yoke in a vise, unscrew the bolts 19, remove the spring washers and separate the washer 20 from the yoke.
Remove the pinion gear and sun gear from the cage.
The front clip and washer cannot be depersonalized during repair, therefore, after disassembly, connect them into a set.
Remove retaining ring 3 from the front cage, press bearing 4 with a puller.
Unbend the tab of the lock washer 13, unscrew the nut 14 and remove the lock washer.
Using a drift with a diameter of 10 mm, with light blows of a hammer through two holes in the rear cage 11, press the bearing 12 assembled with the crankcase 18 from the cage.
Bend the ends of the locking plates and unscrew the bolts 10 securing the rear cage to the gear of the lower shaft, separate the cage from the gear.
Using a soft metal drift, press bearing 12 out of differential rear bearing housing 18.
Using a mandrel, press the collars out of the bearing caps.
Gears may have tooth wear in thickness, chipping and pitting (a rash in the form of small shells) of the cemented surface of the tooth, chips and cracks.
For defects such as cracks and chips on the ends of the teeth with a length of more than 5 mm, chipping with a total area of more than 8 mm2 or pitting covering more than 25% of the working surface of the tooth, the gears should be rejected.
Gears with small (0.5-1.0 mm) chipped ends of the teeth can be used for further work. Sharp edges of chips, as well as burrs on the top of the tooth head, blunt and clean.
Check the wear of the teeth in thickness with a limit gauge or a gear gauge.
Two methods are provided for checking the technical condition of the splines of parts: the first is by measurements using rollers, the second is by measuring the side clearance between the splines in the connection of a worn part with a mating new one.
Assembly of the transfer case is carried out in two steps: first, assemble the nodes, then assemble the box as a whole.
When assembling the box, first install the fork 18 (see Fig. 1) together with the clutch 26, the stem 21 and the shift fork assembly with the stem 23 into the crankcase, then install the remaining components and parts in the reverse order of disassembly.
When subassembling the components and assembling the transfer case as a whole, consider the following.
Assemble the units to the completeness shown in fig. 3-7.
Apply the lubricant used for filling into the crankcase on the gear bushings of the input shaft of the gear and the neck of the shaft 7 (see Fig. 1).
Apply TsIATIM-201 lubricant to the cuffs, mating flange surfaces, bearing journals of gear 10 and gear teeth 8 and 10.
Sealing gaskets and threads in the through holes of the crankcase should be lubricated with a thin layer of sealing lubricant, and in the absence of it with any grease.
After reassembling the units, check the ease of rotation: shafts 24 and 27 in the bearing caps, low gear on shaft 7 and driven gear 10 in the countershaft bearing cap.
Oil rings 6 (see Fig. 5) and 4 (see Fig. 6) differ from each other in the direction of cutting and are marked with the letters “P” and “3”, respectively.
When subassembling the ring assemblies, install: with the marking "3" - on the shaft 24 (see Fig. 1) of the rear axle drive; marked "P" - on the shaft 27 of the front axle drive.
Install flanges on shafts, cuffs and covers using mandrels. Install the lower shaft gear 9 (see Fig. 7) with the elongated part of the hub (with studs) to the front race 1 sun gear 17 with the elongated part of the hub to the rear race 11.
Mount the differential lock clutch on the shaft so that the rounded ends of the splines are directed towards the engagement.
Tighten the main threaded connections of the parts with a torque wrench.
After tightening the nuts and bolts of the critical threaded connections, lock them.
Carry out the locking nuts for fastening the bearings on the shafts and nuts 13 (see Fig. 2) for fastening the drivers carefully, deforming the thin part of the nut into the groove of the shaft.
Adjusting the transfer case
When adjusting the transfer gearbox, two types of work are performed to ensure the verification and, if necessary, the installation of normal axial play of the input and intermediate shafts, as well as the normal position of the gear shift carriage and differential lock clutch.
Axial play is estimated by the total axial movement of the shafts. With the nuts of the shaft bearings tightened, the movement should be for the shafts: primary 0.15-0.20, intermediate 0.08-0.13 mm.
Measure axial play with an indicator, using a mounting spatula to move the shafts (Fig. 10).
When adjusting the axial play of the intermediate shaft, rest the indicator leg against the end of one of the gears.
To avoid errors when measuring axial play, check the play before and after adjustment 2-3 times, first turning the shafts before measuring.
If the axial movement is greater than normal, remove the shims at the input shaft from under the front bearing cover, at the intermediate shaft from under the rear bearing cover.
To ensure bearing adjustment, a shim package is installed at the factory under these covers, in which there are at least four 0.05 mm thick shims and at least three 0.1 mm thick shims.
The position of the differential lock clutch can be adjusted by turning the stem.
When checking the correct position of the coupling, set the rod to the front fixed position and rotate the front axle drive shaft by the flange.
If the clutch does not touch the spline end of the front differential cage, then it is installed correctly. If the clutch touches the cage, move it forward by turning the stem clockwise.
Regulate the position of the shift carriage by selecting a package of shims 17 (see Fig. 1).
Three to six shims 0.2 mm thick are installed between the body for fixing the shift fork rod and the transfer case housing.
The position of the coupling should be considered normal if, with a fixed neutral position of the rod, the difference in the free length of the input shaft splines on both sides of the coupling does not exceed 1 mm.
Transfer case test
After repair, carry out tests to check the quality of assembly and adjustment of the transfer case.
Before testing, fill the crankcase with lubricant up to the level of the control hole.
It is allowed to test on industrial oil I-20A with replacement after testing.
Tests are carried out on a stand at a speed of 1800 rpm of the input shaft, the duration of the test is 20 minutes in each gear.
The gears and the differential lock are switched on and off only after the input shaft has completely stopped.
The differential parts are run on the stand by briefly braking the rear axle drive shaft with a parking brake.
The following are not allowed during testing:
- - sticking and not smooth switching on, gear disengagement and differential lock;
- - knock and uneven noise of gears; lubricant leaks;
- - increased crankcase heating at the bearing installation sites.
After testing on the bench, check the transfer case for leaks.
To do this, apply an air pressure of 0.30 kgf/cm2 to the threaded hole for fitting 11 through a pipeline with a cock into the crankcase and turn off the cock.
The transfer box is sealed if the air pressure drops by 0.15 kgf/cm2 within 2 minutes, no more.
Mounting the transfer case
It is imperative to install the transfer case on the car in the reverse order of removal from the car.
After installing the transfer case on the vehicle, check the adjustment of the control drive and, if necessary, adjust the control drive.
The transfer box control drive should be considered adjusted if the gearshift lever in the neutral position of the rod is in the middle of the length of the opening in the cab floor, and the differential lock lever with the differential unlocked and locked does not reach the front and rear edges of the opening by 10 - 15 mm .
The position of the transfer box control levers along the length of the openings in the cabin floor must be adjusted by changing the length of the rods 11 and 12 (see Fig. 2).