Manual for disassembling and assembling the rear axle of the tractor "BELARUS 1221.2/1221В.2/1221.3/1221.4"

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01.08.2021

The front axle in the MTZ-1221 tractor is a beam reinforced FDA, which in its design includes planetary spur gearboxes of one of two possible brands: 1222-2300020 or 1222-2300020-05. The rotation of the unit occurs due to the built-in drive in the gearbox, which has an electro-hydraulic activation.

FDA device

The front axle assembly of the 1221 tractor is connected to the front of the semi-frame using a swing joint. Moreover, it is a cast prefabricated beam, which consists of three elements connected to each other by flanges. The main gear together with the differential are located in the central part, and the axle shafts are located in the side parts.

On the outer side, the axle shafts are equipped with rotary supports, which are necessary for connection with the housings of wheel-type gearboxes. Through cardan joints, rotation occurs from the axle shafts to the planetary-cylindrical mechanisms.

Main gearbox

The main gearbox of the front axle of the 1221 tractor is made in the form of a main gear consisting of two bevel gears and a self-locking limited slip differential. Gears have helical teeth. The drive is located inside a cup located on two bearings, and the driven is on the splines of the differential housing.

Structurally, the drive gear also includes a shaft. On its shank there is a flange, which is designed for connection with a cardan-type transmission from the FDA drive. The gap between the roller bearings of the cup is adjusted by selecting washers and proper tightening.

The gap for engagement of the pair at the main gear is adjusted by installing gaskets that are installed under the connecting flange of the cup with the flange of the bridge housing in the central area.

Content

Main gear The main gear is a pair of bevel gears with a spiral tooth. Leakage of lubricant through the cuff of the drive gear of the wheel reducer Increased clearance in the gear bearings - Check and adjust. When the coupling half moves, its conical section is lifted by a pusher, which closes the contacts of the hydraulic distributor switch.

These tractors do not have a transfer case as such, and the power take-off to the FDA and the power take-off shaft are carried out from a separate shaft and gear system in the gearbox. The cams of the drum 3 move the coupling half 4 along the shaft splines in the axial direction, compressing the spring 5. The support for the sliding fork of the propeller shaft is installed in the clutch housing.

The frictional force of the compressed disks combines the side gears and the housing with the differential cover into one unit, thus locking the differential. Increased wear and delamination of the front wheel tires. Wheel toe adjustment is broken - Adjust the toe-in. With correctly adjusted bearings, the gearbox should rotate relative to the axes of the pins with a torque of Nm.

If any problems are found, correct them. Refueling of the FDA must be done on a horizontal surface. Adjustments are made with a screw. Tapered roller bearings 18 of flange 1 must be adjusted without play by tightening the nut. Inclusion of ranges and gears in MTZ 1025.2

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Differential

This structural element in the front axle of the MTZ-1221 tractor is mounted on two angular contact tapered roller bearings. The gap between them is adjusted to the connecting flanges from the main gearbox housings and the right axle shaft.

The axle differential is a unit consisting of two semi-housings held together by eight bolts. The housing includes the following set of components:

• prefabricated cross with 4 satellites having spherical ends;
• 2 semi-axial gears with couplings to block increased friction between parts.

The rotation from this element is transmitted to the cardan transmissions (left and right) due to the cardan shafts, which enter with splined ends inside the splines of the semi-axial gears. In this case, the external ones are embedded in the shanks of the cardan gear forks from the drive of the final drives.

The support of the wheel final drives by the housings is organized on 2 vertically located turning points, which are equipped with conical angular contact bearings. The gap is adjusted using a pack of shims located on the upper and lower supports.

Need for gearbox repair

When is gearbox repair required? Special equipment should be diagnosed if the transmission starts to switch off spontaneously. Another problem that a tractor owner may encounter is difficult lever movement.

Gearbox 1221 MTZ disassembled

Repair of the MTZ gearbox may consist of replacing:

• oils;
• backstage;
• bearings;
• grooves and other components of gearbox consumable spare parts.

Repairs may involve tightening loose fasteners, which may cause noise from the box. Also, the cause of noise is wear of the bearings. In parallel with this, overheating of the gearbox may occur. To replace the bearings, the oil is drained, the box cover is dismantled, then the gearbox itself, after which it must be disassembled.

When gear teeth wear, a characteristic sound is noted. In good condition, no knocking noises should be heard from the gearbox.

In some cases, it is necessary to flush the existing oil strainer. Washing should be done in clean diesel fuel. One of the frequent breakdowns is the presence of a low oil level in the box. It should be on the bottom edge of the existing inspection hole. The fuel level is checked when the equipment is standing on a level surface. In this case, the engine must be warmed up. Add liquid through the filler plug on the top cap.

Front axle device

The cylindrical idler gear is mounted with its side facing outwards on a bearing inside the cup. The element is designed to provide rotation in the direction from the cardan joint to the wheel gearbox. The gear support is secured by tightening the cup using a pack of shims to ensure the required clearance at the gear bearings.

Further in the direction from the intermediate gear, rotation goes to the planetary region of the wheel gearbox. In this case, the planetary mechanism itself is located on the hub flange shaft. On its side, the shaft rests on a conical roller bearing. The carrier hub is mounted on the splined part of the flange shaft. And on the inside there is a cylindrical block that includes two gears.

The large gear is driven and receives drive from the intermediate spur gear. The small one is of the solar type and is included in the planetary mechanism on the carrier hub. It is responsible for transmitting rotation to 3 satellites, which are installed on the axles of the carrier outside. At the same time, the axles themselves are rolled along the crown of the epicycle with teeth, which is pressed inside the gearbox cover.

The gear block rests on a double-row spherical roller bearing. It is fixed in two ways at the same time: on the shaft and the block using retaining rings. In this case, the inner end of the shaft rests on a cage from a tapered roller bearing installed in the cup. All structural elements are tightened with a nut and a cup lid with 4 bolts.

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Organization of front axle operation

Let us describe the operating procedure of the wheel gearbox step by step:

• semi-axial universal joints transmit rotation to the drive spur gear;
• then the gear block located on the bearings of the flange shaft begins to rotate;
• the sun and driven gears inside a single block transmit further rotation to the satellites;
• the rolling of the last components along the crown of the epicycle carries with it the carrier of the planetary mechanism;
• then the flange with the running wheel rotates.

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Differences between the front axles of MTZ-1221 tractors

As mentioned above, the front axles for the MTZ-1221 tractor can correspond to one of two markings: 1222-2300020 and 1222-2300020-05. For this reason, it is important to know the differences between them. They are part of wheel gearboxes. Therefore, the configuration of both the front and rear axles directly depends on these components. If the gear ratios of the drive axles do not match, drive synchronization is not achieved, which can subsequently lead to uneven wear on the front tires, as well as the formation of loads inside the FDA and drive mechanisms.

The nodes differ in the following components:

• gear housings;
• cylindrical gears, which are driven by a semi-axial universal joint;
• gear block of sun and driven gears.

The first model of the front axle of the 1221 tractor is equipped with a gear that receives rotation from a 17-tooth axial universal joint. In the second case, the process is ensured by transmission of rotation to 14 teeth. In this case, the driven gear of the first front axle contains 44 teeth, and the second - 40 teeth.

Malfunctions and methods for their elimination

To repair the MTZ-1221 front axle, it is necessary to first diagnose the cause of the malfunction. In case of physical damage to the gears of the gearboxes or the main drive, the FDA will have to be completely disassembled. However, in most cases, to carry out repairs, it is enough to disassemble only part of the assembly or limit ourselves to adjustment and adjustment activities. Main types of faults and repair methods:

Insufficient front axle traction. Occurs due to incomplete transmission of torque or its absence at all. There are several possible reasons: wear of parts due to oil leakage in the hydraulic system and a malfunction in the electrical circuit. In the first situation, it is necessary to replace faulty elements and adjust the oil level and pressure. If it does not work for the second reason, replacing the damaged electrical components will solve the problem. Automatic activation of the FDA drive does not work. Probable cause: the auto-on sensor switch is not adjusted or has failed; replacement or adjustment is required. Loud noise and increased heating in the area of ​​the main gear are caused by play in the bearings or improper meshing of the gears. Repair method: making the necessary adjustments. Lubricant leakage. In most cases, it is caused by wear of the cuff where the oil appears. The repair is simple - replacing the cuff. The exception is leakage through breathers in wheel reduction gears. This indicates an increased oil level. Noise at maximum wheel turn. Occurs when the bridge operates in forced mode. As a repair, it is proposed to set the corresponding switch to the “Off” position. or "Automatic". Knock in the front axle kingpin when driving. Occurs when bearings are not adjusted correctly. To fix it, just adjust them.

The front drive axle is a reliable mechanism with a long service life, so failure is rarely sudden. To prevent situations where the FDA fails at the most inopportune moment and repairs have to be carried out in the field, it is necessary to carry out routine maintenance of the unit in a timely manner and promptly respond to any extraneous sounds emitted by the front axle: most faults are easily diagnosed by ear.