Two-axle semi-trailer MAZ-938 (Fig. 1) with a metal deck with a carrying capacity of 13 tons, and MAZ-938B (Fig. 2) with an elongated frame without a deck with a carrying capacity of 13.5 tons

Semi-trailers are designed for installation of various equipment and operation on various types of roads, including exit and short-term off-road driving. King pin diameter 50.8 mm.

The main traction vehicle for towing is the KrAZ-255V truck tractor and others.

General view of MAZ-938 semi-trailer


Frame of the MAZ-938 semi-trailer is a welded structure made of sheet metal and stamped profiles. The main load-bearing elements of the frame are made of low-alloy steel.

The front of the frame is raised above the fifth wheel of the tractor compared to the main bearing surface of the frame.

Spars of the I-section frame, welded, with increased wall height in places of maximum loads.

To reduce stresses and increase wall rigidity, corner reinforcements are welded at the frame transition. The side beams of the frame are stamped, channel section.

General view of MAZ-938B semi-trailer:

The beams and spars are connected by cantilevered cross-sections of variable section, made with stamped holes to reduce the weight of the frame.

In the front part, a reel plate is welded to the spars, on which a kingpin socket with a pressed kingpin is welded between the crossbars.

Brackets for fastening support devices are welded to the side member wall at the transition point.

In the rear part of the frame, to the side members with rivets 16x52 mm, the brackets of the balancer suspension are attached, interconnected in pairs by pipes, the brackets of the balancer axle and the brackets of the suspension buffer.

Mooring eyes are welded to the spars, which serve to fasten the semi-trailer during its transportation by various modes of transport.

To store tools and accessories, a tool box is fixed between the side members in the transition zone.

The upper surface of the frame is covered with a welded corrugated steel deck, which increases the strength of the frame and ensures the convenience of moving the load along the frame during loading and unloading.

In the area of ​​the wheels of the semi-trailer, the frame beam is cut and connected to the side member by crossbars and beams for attaching sliding wheel niches.

The frame of the semi-trailer MAZ-938B is the same in design as the frame of the MA3-938. The difference is:

  • - longer spars and frame beams, which increases the length of the loaded part up to 9160 mm;
  • - the flooring and fastening parts of the wheel arches are not installed;
  • - the total length of the frame is 13040 mm.

The diameter of the kingpin for the grips of the tractor fifth wheel is 50.8 mm.

Maintenance and repair are the same as the frames of the MAZ-5245 semi-trailer, except that if cracks appear in the places where the flooring is welded, it is necessary to clean the places of damage and weld them by electric arc welding with an electrode Ø 2-3 mm.


Device. The semi-trailer is equipped with an independent lever spring-balanced suspension.

The design of such a suspension consists, as it were, of two systems: a lever and a spring-balancer.

Link suspension

The link suspension system (Fig. 3) provides independent suspension of each wheel, which is necessary to create good wheel adaptability to road irregularities.

Each wheel has a guide device representing a four-link trapezoidal type, formed by a suspension bracket 6, lower 5 and upper 18 levers and a suspension rack 1.

The guiding device provides the ability to move the wheel only in a vertical plane, perceives and transmits pushing forces from the frame to the wheels and the braking moment from the wheels to the frame.

The suspension arms 5 and 18 are connected to the wheels of the semi-trailer through the rack 1, to which the wheel trunnion is attached. The levers with the rack are pivotally connected with the help of fingers 13.

The suspension arms are connected to the frame through suspension bracket 6. The levers with the bracket are pivotally connected using axles 8.

Axles and pins from turning are locked in the bracket and rack with wedges 16 and 12, secured with nuts 11.

Bronze bushings 21 are pressed into the holes of the levers under the pins and axles, for lubrication of which oilers 19 are provided. For better distribution of lubricant along the bushing, a helical groove 5 mm wide and 1 mm deep is made on its inner surface.

Sufficient rigidity of the link suspension system will ensure it is welded with pipes of brackets: top 17 with a diameter of 106 mm and bottom 7 with a diameter of 68 mm, which are pressed into brackets 6.

Bar suspension system

The spring-balancing part of the suspension (fig. 4) ensures even distribution of the load between the wheels located on one side of the semi-trailer.

Spring 8, which serves both as a balancer and an elastic element, with its ends located between the upper and lower levers and rests on spherical supports 7, which are mounted on support brackets 2 (see Fig. 3).

The spherical surface of the supports 7 (see Fig. 4), mating with the lower main leaf of the spring, dramatically reduces leaf wear.

Support brackets 2 (see Fig. 3) are pressed into the wheel trunnions and welded to them.

Moving the wheel down when they hover is limited by brackets 1 limiters 4, fixed on the support bracket 2.

The spring with its middle part is attached to the balancer 6 (see Fig. 4), which has a platform for installing the spring. At the ends of the platform, tides are cast, limiting the lateral displacement of the spring.

The hole in the body of the balancer is made stepped: for bushings 27 - with a diameter of 132-0.08 mm and for the stuffing box 15 - with a diameter of 175 + 0.08 mm.

Six holes with M8 thread were drilled on the outer flange of the balancer for attaching cover 4.

There is a sealing gasket 25 made of cardboard 0.8 mm thick between the balancer and the cover.

The cover has a threaded hole, closed with a plug 19, for pouring oil into the internal cavity of the balancer.

Install cover 5 in such a way that the hole for the plug is above the axis of the balancer.

The plug hole determines the oil level in the balancer, and therefore it is not allowed to change the position of the cover.

The balancer with two bronze bushings pressed into it oscillates about the axis 26 of the balancer.

The balancer is fixed against axial displacement by thrust rings 16 and 17, spacer sleeve 14, nut 18, lock washers 22 and lock washers 23 and locknut 20.

The nut is tightened so that the balancer can be turned by hand.

In the drilling of the body of the nut 18, a pin protruding above its surface by 4.5 ± 0.5 mm is pressed in.

A lock washer 23 is installed on the pin and the axis of the balancer, the protrusion on the inner hole of which enters the groove milled along the threaded sheikh of the axis.

The lock washer 22 of the lock nut is installed with a special extrusion into the hole of the lock washer 23, after which the lock nut 20 is screwed onto the axle. The mustache of the lock washer is bent onto the face of the lock nut.

The bushings 27 of the balancer are made of bronze and are finished after being pressed into the balancer.

To ensure optimal distribution of the lubricant along the relatively long neck of the balancer axis, the surface of the bronze bushings is provided with helical grooves 1 mm deep.

The axis of the balancer is made of steel pipe 127Lx24-45.

The necks for the holes in the brackets have a diameter of 124-0.08 mm, and the necks for the installation of balancers have a diameter of 122-0.06 mm.

Brackets 2 of the balancer axle are attached to the semi-trailer frame using bolts 11.

The brackets are pressed onto the journals of the axle 26 and welded to it through the windows located on the walls of the tide for the hole for the axle journals.

Protection against dust and dirt on the rubbing surfaces of the balancer is carried out on one side of the balancer using a cover 4 with a gasket 25, and on the other - an oil seal 15 with a sealing ring 12 and a safety washer 13.

Moving the wheel upwards is limited by the buffer bracket 15 installed on the side member (Fig. 3), against which the platform of the upper suspension arm rests.

The rubber buffer 14, mounted on the balancer bracket, serves to mitigate shocks.

When the wheel moves up, the spring turns on the balancer axis until it stops against the protrusion on the balancer bracket.

In the future, the upward movement of the wheel occurs due to the deformation of the spring until it stops in buffer 14.

The spring is attached to the balancer using two ladders 10 (see Fig. 4). A pad 9 is installed between the ladders and the spring.

The inner surface of the lining is made along the radius and fits snugly against the spring.

On the outer surface of the lining, there are two transverse grooves that fix the relative position of the ladders.

A hole is drilled in the center of the pad to accommodate the spring center bolt nut. The ends of the ladders are fixed in the holes of the balancer with high nuts.

The spring consists of a package of sheets that are tightened with a center bolt.

The main sheets of the spring are of the same length and are fixed with each other by an extrusion along the perimeter of the hole for the center bolt in such a way that the protrusion of the upper sheet enters the recess of the lower one.

To prevent lateral movement of the sheetov are two clamps, made of strip steel, riveted at the ends of the leaf spring.

To prevent the ends of the clamp from bending, a 104 mm spacer tube is installed between the cheeks of the clamp with a coupling bolt.

Suspension maintenance is to check the tightness of all bolted connections.

It is especially necessary to monitor the fastening of the balancer axle brackets to the semi-trailer frame and the tightening of the spring ladders, as well as the condition of the fasteners of the elements of the suspension linkage system.

In order to prevent shearing of the center bolt of the spring, it is necessary to tighten the nuts of the ladders with a torque of 60 - 65 kgcm.

When installing the balancer on the axle or loosening its fastening, first tighten the balancer nut until it stops, and then loosen it by 112 turns, while the balancer must rotate on the axle by hand.

After that, the nut should be secured with a lock washer 23 (see Fig. 4), put on the lock washer 22 and tighten the lock nut 20, locking it with the lock washer.

In no case should a semi-trailer be allowed to operate with an increased axial play of the balancers, as this can lead to a break in the threads on the axle and nuts.

Suspension maintenance, in addition, comes down to mandatory lubrication of the spring leaves with graphite grease during their next disassembly, adding oil to the balancer cavity and lubricating the fingers of the suspension arms.

Repair. Disassembly of the suspension of the left and right wheels is performed simultaneously.

To disassemble the suspension, it is necessary, having installed the rear part of the frame on the goats, to remove the wheels, limiter brackets, spring ladders and springs.

If it is necessary to remove the balancer, unscrew the drain plug, turn the balancer with the drain hole down and drain the oil from the balancer, then remove the balancer cover, unscrew the lock nut, remove the lock and lock washers, unscrew the nut and remove the balancer.

The axle of the balancer with the brackets as an assembly is removed in case of breakage of the axle or the bracket of the balancer.

If it is necessary to disassemble the guide device, it is necessary to unscrew the nuts of the wedges of the pins and the axles of the upper and lower levers, knock out the wedges, remove the covers of the pins and the axles of the upper and lower arms, knock out the pins and the axles of the levers.

During operation, leaf breakage and cracks, breakage of the center bolt, breakage of clamps, wear of the ends of the main sheet may occur in the springs.

Spring sheets with cracks or wear from the mating sheet of more than 1 mm should be rejected.

Broken center bolts and clamps must be replaced.

Cracks on the clamps are welded and cleaned flush with the main surface. Worn lower root leaves, swapped with second root leaves.

Root sheets with wear of more than 6 mm are replaced with new ones.

In the presence of cracks and slight wear, the leaf springs can be converted to shorter ones and used to assemble the springs.

Sheets with residual deformation (sagging) are straightened, ensuring the dimensions of the sheets.

Step-ladders that have cracks or stripped threads are replaced with new ones, and cracked spring pads are welded and cleaned.

When stripping the spring, the following requirements must be observed:

  • - the spring sheets must fit tightly to each other, the gaps between the assembled spring sheets are allowed for a length of no more than ¼ of the total contact length of two adjacent sheets, while the gap should not exceed 2 mm.

Attention of the working ends of the sheets is required.

Each spring after assembly is subjected to a draft to a deflection of 160 mm from a free state (under a load of approximately 19500 kgf).

Repeated loading of the same magnitude must not cause permanent deformation.

From the control load of 7850 kgf, the deflection should be 88 mm. The ends of the springs are supported on cylindrical supports with a radius of 100 mm;

  • - Lubricate the rubbing surfaces of the sheets with graphite grease before assembly;
  • - after tightening the nuts, the threaded ends of the clamp bolts and center bolts should be punched or riveted.

Clamps of springs should not interfere with the free movement of sheets during operation of the spring;

  • - offset of the spring sheets in width relative to the first sheet is allowed no more than 2.5 mm.

The spring assembly is subjected to a draft, after which it is sorted into two groups depending on the deflection arrow: the 1st group includes springs with a deflection arrow of 123 +10 mm (they are marked with white paint), which 2nd - with a deflection arrow 123-10 mm (they are not marked).

Only one group of springs is installed on the semi-trailer.

In the balancer suspension and the wheel guide, the bushings, balancer axle, balancer seals, pins and axles of the suspension arms wear out.

Thoroughly clean bronze bushings from old grease and dirt. Thoroughly clean rust, arson and enveloping of bronze with emery cloth.

Worn balancer bushings are pressed out and replaced with new ones. But After pressing, the outer bushings are bored to size 122+008 mm.

Possible suspension failures and how to fix them

Cause of malfunction - Remedy

Spring leaf shift:

Center bolt sheared - Replace center bolt

The end of the spring touches the support bracket:

Ball joint wear - Replace ball joint

Oil leak in balancer:

Worn seal or bad seal - Replace seal or seal

Lack of oil in the balancer in the absence of a leak:

Oil from the balancer goes into the axis of the balancer - Restore the tightness of the plug of the balancer axis by welding

Suspension strut pitching in the arm:

Thrust washers worn - Replace thrust washers

Increased spring settlement:

  • - Broken individual sheets - Replace broken sheets
  • - Loss of elasticity of sheets - Straighten sheets

The same is done with lever bushings with a bore for size 90 +0.07 mm.

Welding cracks in the places where the balancer axle is welded to the suspension bracket are not a defective sign and can be eliminated by additional welding.

The working edge of the seal must be sharp, without dents, cracks or other damage.

Oil seals with the indicated damage must be replaced with new ones. O-rings and gaskets must be intact.

Axle with hub

When assembling the suspension balancer with the axle, the following requirements must be observed.

Install a safety washer 13 (see Fig. 4), a spacer sleeve 14 with a sealing ring 12 on the balancer axle, install a thrust ring 16 and an oil seal 15 into the balancer, then, after lubricating the axle of the balancer bushing with transmission oil, install the balancer on the axle .

After installing the thrust ring 17, tighten the balancer nut so that the balancer rotates on the axis with a slight hand effort without noticeable longitudinal play.

Install the lock washer so that its hole aligns with the pin of the nut.

Install the lock washer of the lock nut with the protrusion into the hole of the lock washer of the nut.

3 Tighten the lock nut to failure and lock it by bending the edge of the washer onto the face of the nut.

Pour MT-16P oil (GOST 6Z60-58) into the assembled balancer along the lower edge of the filler hole (0.6-0.7 l each).

Assembly of the guide device and installation of the spring on the semi-trailer is carried out in the reverse order of disassembly and removal.

The tightening torque of the nuts of the bolts for fastening the brackets of the balancers to the frame should be 12-14 kgf•m.

Axles and hubs

Axle 11 (fig. 5) of the wheel is bolted to the rack 12 of the independent suspension of the semi-trailer.

The support bracket 13 of the spring is pressed into the axle. Caliper 14 of the brake is attached to the axle with bolts

Wheel hub 1 is mounted on two tapered roller bearings.

The wheel is fastened to the hub using nuts 6, clamps 7 and bolts.

Maintenance of the axle and hub is the same as for similar parts of the MAZ-5245 semi-trailer.

Wheels and tires

Device. The semi-trailer is equipped with discless wheels (Fig. 6) 440-553 mm in size with tires 1300x530x533 model VI-3.

Semi-trailer wheel

The tires are 12-layer low-pressure pneumatic cylinders with a directional tread pattern.

The tire is clamped between the bead rings 1 using the locking ring 3.

Valve 11 of the wheel chamber is connected to the centralized tire inflation valve using cap nut 13.

The connection is sealed by pressing the rubber sealing ring 12.

For the purpose of unification and interchangeability of the wheels of the tractor with the semi-trailer, a wheel valve 6 is installed on the wheels of the semi-trailer, which is included in the centralized tire pressure control system on the tractor.

The tires of the semi-trailer wheels are inflated through valve 4 for individual tire inflation. Plug 5 must be screwed in as far as it will go.

Maintenance of the wheels and the basic rules for operating tires are the same as for the MAZ-5207V trailer.

Mounting and removing wheels

To remove the wheel from the semi-trailer, use a hydraulic jack to raise it 5-10 cm above the ground, unscrew the nuts of the hub bolts and carefully, without touching the threaded part of the bolts, remove the wheel, after moving the sliding wheel niche.

Install the wheels in reverse order.

When installing the wheel on the hub and fixing it, it is necessary to ensure that there is no end runout of the wheels, which is controlled by fitting the adjusting ring 7 (see Fig. 6) on the hub.

The difference in landing sizes for diametrically opposite hub spokes should not exceed 4 mm.

Mounting and demounting the tire on the rim is performed using two mounting blades.

The installation order is as follows.

Insert the inner tube 10 into the tire, after powdering them with talcum powder, insert the rim tape and lightly inflate the inner tube with air.

Place the wheel rim 8 on a clean floor with the valve groove up, put on the bead ring 1 and then the tire 9 on the rim.

In this case, the chamber valve should come out through the groove of the rim and be located in the center of the hole in the protective cover welded to the rim.

Put on bead ring 1, insert seat ring 2 so that the locking lug on the seat ring is in the widened part of the valve groove.

Insert the bent end of the mounting spatula into the keyway of the rim and push the seat ring down, thereby freeing the keyway of the rim for seating the keyring.

Insert one end of the lock ring 3 into the lock groove of the rim and with the straight end of the mounting blade inserted between the rim and the lock ring, press the ring towards you until it is fully installed.

Fix the wheel crane 6 on the rim guard, for which:

  • - remove the valve from the opening of the casing and put on it a union nut, a conical washer, a sealing ring, a faucet fastening nut and a spring washer;
  • - insert the wheel valve into the opening of the casing and insert the end of the valve into the valve cavity, preventing dust and foreign objects from entering;
  • - put on a spring washer, screw on the nut that secures the valve to the casing, without tightening it, screw on the union nut. In this case, the sealing ring and the conical washer must enter the inside of the nut without distortions and pinches;
  • - tighten the faucet fastening nut and the union nut (overtightening the union nut can lead to deformation of the valve).

Close the wheel valve (if it was open) by screwing the stopper 5 with a special wrench and inflate the tire to the required pressure through the individual inflation valve.

When inflating a tire in a garage, the assembled wheel must be placed in a special grate, and when this operation is performed outside the garage, the locking part of the wheel must be directed away from the driver and people nearby.

Cold tires must be warmed up to positive temperature before installation.

When mounting tires with a directional tread pattern (off-road), ensure that the direction indicators for their rotation (arrows on the sidewalls of the tires) coincide with the direction of rotation of the wheels when the vehicle is moving forward.

It is recommended to remove tires in the following order.

Leave the air out of the tire, remove the wheel valve 6, insert the bent end of the mounting blade into the stamped groove of the seat ring 2 and push the tire bead together with the bead ring.

Repeating this operation on each groove, sequentially around the circumference of the wheel, completely remove the tire bead from the landing flange of the ring.

Remove lock ring 3, for which:

  • - insert the straight end of the mounting blade into the groove of the key ring and press the seat ring down;

Insert the bent end of the second mounting blade into the resulting gap between the key and seat rings and, sequentially pressing it around the wheel circumference, push the seat ring down;

  • - with the straight end of the mounting blade, press the lock ring and remove it from the groove, and with the curved end of the second mounting blade, sequentially remove the lock ring from the groove until it is finally removed.

Insert the bent end of the mounting blade between the bead ring and the shoulder of the seat ring and press the seat ring sequentially around the circumference of the wheel until it is finally removed.

Remove the bead ring 1, turn the wheel over and remove the tire bead from the seat.

Place the wheel obliquely against the wall and, inserting the curved end of the mounting blade between the bead ring and the shoulder of the rim, slightly squeeze the rim around the circumference.

Holding the rim with both hands, completely remove it, having previously sunk the valve into the groove of the rim.

In case of sticking (burning) of the rim tape to the rim, it is necessary to turn the wheel over, insert the straight end of the mounting blade between the rim and the rim tape and, moving it around the circumference, completely release the rim tape.

Reference Device

Adjusting the wheel bearings. At each TO-2, it is necessary to check and, if necessary, adjust the tightening of the wheel hub bearings.

Adjust the bearings in the following order.

Raise the wheel with a jack so that the wheel tire does not touch the ground.

Unscrew the bolts securing the hub cover, remove the cover 4 (see Fig. 5). Loosen the lock nut, remove the lock washer 3 and check whether the wheel rotates freely.

If the wheel is hard to turn, you need tofind out the cause and eliminate it (brake lining grazing, bearing failure).

Tighten the nut to failure with a force of approximately 40 - 50 kgf on a wrench with a 500 mm wrench.

When tightening the nut, rotate the wheel to properly position the rollers on the raceways of the bearing rings.

Unscrew the nut by one or two slots in it until the tab of the lock washer aligns with the slot of the nut, then check the rotation of the wheel; wheel - should rotate freely, but without axial play.

Install the lock washer and tighten the locknut until it stops.

After adjusting the tightening of the wheel hub bearings, check the correctness of the adjustment by heating the hub cover during the first 100 km of run.

Heating the hub to a high temperature (the hand cannot withstand prolonged contact) is not allowed and must be eliminated by re-adjusting the bearings or brakes.

Repair. Tires and tubes are repaired by vulcanization. Cracks may appear on the wheel rims during operation. Cracks are cut, welded and cleaned flush with the main surface.

To prevent the crack from spreading, the ends of the crack are drilled before welding.

Reference device

Device. The supporting device (Fig. 7) consists of two screw jacks (Fig. 8) located in the front of the semi-trailer and interconnected by an intermediate shaft.

The right support device differs from the left one in the presence of a two-speed gearbox.

The presence of a two-speed gearbox provides accelerated lifting and lowering of the plates of supporting devices at idle.

The uppermost position of the retractable stand of the supporting device is limited by the bushing on the fixed stand 6. The lowest position is limited by the shoulder 3 of the screw.

In order to raise the semi-trailer (i.e. extend the mobile stand to the lower position), you must:

Prop Jack

  • - install the semi-trailer on a horizontal platform and use the steering wheel 1 (see Fig. 7) to pull the drive shaft 23 towards you (see Fig. 8) until the ball 32 enters the annular groove, thereby engaging the overdrive;
  • - turning the steering wheel counterclockwise, lower the support device until the base plate 2 touches the ground;
  • - turn on a downshift, for which, move the drive shaft forward to failure with the steering wheel from yourself and, turning the steering wheel counterclockwise, raise the semi-trailer.

Lowering the semi-trailer or setting the support device to its original position is carried out in reverse order.

When lifting the semi-trailer (lowering the supporting devices), pawl 5 (see Fig. 7) must be engaged with the ratchet of the intermediate shaft 4.

When lifting the support devices to the transport position, the pawl must be disengaged.

Working in second gear (the drive shaft is extended to failure) after the plate touches the ground (regardless of whether the semi-trailer is loaded or not) is strictly prohibited.

In exceptional cases, if it is necessary to uncouple the tractor from the semi-trailer on uneven ground, the semi-trailer is provided with a mismatch in the operation of the supporting devices.

If, when lowering the support devices, the base plate of the left support device came into contact with the ground, and the right support device did not reach the ground by more than 50 mm, you must:

  • - engage the pawl 5 with the ratchet of the intermediate shaft 4, remove the pin 7 in the area of ​​the right support device and lower the right support device with the steering wheel until the plate touches the ground;
  • - insert pin 7 and use the steering wheel to raise the semi-trailer to the required height.

If the plate of the right support device is in contact with the ground, and the left one does not reach the ground by more than 50 mm, you must:

  • - engage the pawl 5 with the ratchet of the intermediate shaft 4, remove the pin 7 in the area of ​​the right support device and use the steering wheel to raise the right support device by an amount equal to the distance between the ground and the plate of the left support device;
  • - insert pin 7 and lower the supporting device with the steering wheel until it touches the ground, and then raise the semi-trailer to the required height.

In the future, after coupling the semi-trailer with the tractor, raise the support devices to their original (before the mismatched operation of the support devices) state.


The supporting device must be kept clean.

It is necessary to lubricate the points of the support device to be lubricated in a timely manner, make sure that in the transport position the base plate 2 (see Fig. 8) rests against the protective cap 36 to protect against dirt from under the wheels of the tractor.

In winter, when parking a semi-trailer without a tractor, to prevent freezing of the base plates of the supporting devices under them put wooden linings.

Before working with the support device, it is necessary to break off the ice from the support plates.

Check bolted connections in time and tighten if necessary.


The support device is usually disassembled when replacing worn or broken parts, as well as to add or replace lubricant.

Disassembly can be carried out partially or completely, depending on which part needs to be replaced.

The order of disassembly is as follows:

  • - install the semi-trailer with its front part on the gantry, remove the support devices from the semi-trailer and the steering wheel, turning the drive shaft 23 counterclockwise (see Fig. 8), lower the base plate 2 by 80-100 mm;
  • - remove the locking ring 35, remove the base plate together with the ball joint, unscrew the locking screw 33 and the screw bolt, remove the key with the cover 34 and the covers 14 and 22;
  • - disassemble the drive 23 and driven 11 shafts, unscrew the nut 15, and lightly tapping the hammer on the end of the screw 4, remove the bevel gear 8;
  • - unscrew the bolts 12, remove the body 9 and thrust bearing 7, remove the rack 5, unscrew the rack nut and remove the screw with the nut. The nut with the screw is not disassembled, as it is installed in the kit by the manufacturer;
  • - remove two spherical washers.

After disassembly, wash all parts, blow dry with compressed air, generously lubricate and assemble the support device in reverse order. Fill the crankcase and housings with grease.

Disassembly and assembly of the left support device is carried out similarly to the right one, without taking into account the additional gearbox.

The left support device does not have a brake device, therefore, when removing it from the semi-trailer, it must be lowered until it touches the ground.

Before dismantling the drive shaft, it is also necessary to lower the support device to contact with the ground, since when the shaft is disassembled, the braking device stops.

The drive shaft or parts on it can be replaced without removing the supporting device from the semi-trailer. To replace the drive shaft 23 or any part located on it, you must:

  • - remove the rubber cap and gearbox cover 22, unscrew the nut 19 and sleeve 20, remove the thrust bearing 29, unscrew the plug 31 and remove the ball retainer spring;
  • - turning the drive shaft 23 clockwise with the handwheel, unscrew it from the gear block 28, remove the drive shaft from the gearbox housing, remove the gear block 28, friction ring 27, brake ratchet 26 and ball 32 from the crankcase.

Assembly of the drive shaft should be done in the following order:

  • - install the drive shaft in the hole of the gearbox housing;
  • - install the brake ratchet, friction ring and gear side on the drive shaft;
  • - engage the pawl with the brake ratchet and, holding the gear block with your left hand, screw in the drive shaft with your right hand, turning the steering wheel counterclockwise;
  • - move the drive shaft forward until it fails until it engages with the gear unit of the driven shaft 11, put the ball and retainer spring, screw in the plug, install the thrust bearing, wrap the bushing, lock it with a nut and install the cap.

To disassemble the driven shaft 11 you need:

  • - remove the support device and then the covers 14 and 22;
  • - dismantle the drive shaft 23, remove the bearing cover 18 and remove the thrust ring 13;
  • - install a bronze or brass drift into the mountains of the driven shaft from the side of the gearbox housing and lightly tap the shaft together with the bearing, shims, bearing cover and felt ring;
  • - remove the bearing, shims, bearing cover and felt ring from the driven shaft;
  • - remove the drive bevel gear, key, driven gear set, spacer sleeve and ratchet pawl from the housing;
  • - remove the gearbox housing bearing. The inner bearing of the drive bevel gear does not need to be removed. If it is necessary to replace it, unscrew the bolts and remove the gearbox housing together with the shims 10.

Before assembling the driven shaft, all parts must be washed, blown with dry compressed air and lubricated.

Assembly must be done in the following sequence:

  • - install the key on the driven shaft and engage the drive bevel gear with the driven gear;
  • - insert the shaft into the drive bevel gear and bearing, and then install the driven gear set, spacer and brake ratchet pawl on the shaft;
  • - install the bearings in the gearbox housing and the support device housing and screw the bearing cover 18 to failure;
  • - check the meshing of the bevel gears, adjust if necessary with shims 10;
  • - put the bearing cover with felt ring and insert thrust ring 13 into the annular groove;
  • - assemble and install the drive shaft, fix covers 14 and 22.

Gears, bearings, in Lubricate the screw, nut, internal machined and all friction surfaces of the support device with CIATIM-201 grease.

Brake system

The semi-trailer is equipped with two brake systems: working and parking. Both systems act on the wheel brake pads.

The pneumatic drive of the service brake system, wheel brake mechanisms and parking brake are the same as on the MAZ-5205A semi-trailer.

Electrical equipment

The electrical equipment of the semi-trailer consists of one seven-pin and four single-pin sockets for portable lamps, two rear lights that work as stop signals, side lights, direction indicators and wires connecting the electrical equipment of the tractor and the semi-trailer.

Possible malfunctions of the support device and how to eliminate them

Cause of malfunction - Remedy

When turning the handwheel, the supporting device does not lower or rise

The key on one of the bevel gears has been sheared - Replace the key

Does not hold support device brake

Failure of the screw-nut pair - Replace the screw-nut pair

Friction ring wear - Replace friction ring