The transmission of MTZ tractors uses traditional differentials and final gears that transmit torque to the wheels or wheel gearboxes using axle shafts. Read all about MTZ final drive shafts, their types and designs, as well as their selection and replacement in this article.
What is the final drive shaft of MTZ?
The final drive shaft of the MTZ (drive axle differential shaft) is a component of the transmission of wheeled tractors manufactured by the Minsk Tractor Plant; shafts that transmit torque from the axle differential to the wheels (on the rear axle) or to the vertical shafts and wheels (on the front drive axle, PWM).
The transmission of MTZ equipment is built according to the classical scheme - the torque from the engine through the clutch and gearbox enters the rear axle, where it is first converted by the main gear, passes through the differential of the usual design, and through the final gear enters the drive wheels. The driven gears of the final drive are directly connected to the axle shafts that extend beyond the transmission housing and carry the hubs. Therefore, the rear axle shafts of the MTZ perform two functions at once:
- Transmission of torque from the final gear to the wheel;
- Wheel fastening - its holding and fixation in both planes (the load is distributed between the axle shaft and its casing).
On all-wheel drive modifications of MTZ tractors, PWMs of non-standard design are used. The torque from the gearbox through the transfer case enters the main gear and differential, and from it it is transmitted through the axle shafts to the vertical shafts and wheel drive. Here, the axle shaft does not have direct contact with the drive wheels, so it is only used to transmit torque.
MTZ axle shafts play a key role in the normal functioning of the transmission, so any problems with these parts lead to complication or complete impossibility of operating the tractor. Before replacing the axle shafts, it is necessary to understand their existing types, design and characteristics.
Types, design and characteristics of MTZ final drive axle shafts
All MTZ axle shafts are divided into two groups according to their purpose:
- Front drive axle shafts (PWM), or simply front axle shafts;
- The axle shafts of the final drive of the rear axle, or simply the rear axle shafts.
Also, the details are divided into two groups of origin:
- Original - produced by RUE MTZ (Minsk Tractor Plant);
- Non-original - produced by the Ukrainian enterprises TARA and RZTZ (PJSC "Romny Plant" Traktorozapchast "").
In turn, each of the types of axle shafts has its own varieties and characteristics.
MTZ axle shafts of the front drive axle
The PWM axle shaft occupies a place in the horizontal body of the bridge between the differential and the vertical shaft. The part has a simple design: it is a metal shaft of variable cross-section, on one side of which there are splines for installation in the cuff of the differential (semi-axial gear), and on the other - a bevel gear for connection with the bevel gear of the vertical shaft. Behind the gear, seats with a diameter of 35 mm are made for bearings, and at some distance there is a thread for tightening a special nut holding a package of 2 bearings and a spacer ring.
Two types of axle shafts are used on tractors, the characteristics of which are given in the table:
| Axle shaft cat. number 52-2308063 ("short") | Axle shaft cat.number 52-2308065 ("long") | |
|---|---|---|
| Length | 383 mm | 450 mm |
| Bevel gear diameter | 84 mm | 72 mm |
| Number of bevel gear teeth, Z | 14 | 11 |
| Thread for the locking nut | M35x1.5 | |
| The diameter of the spline tip | 29 mm | |
| Number of tip slots, Z | 10 | |
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Thus, the axle shafts differ in the length and characteristics of the bevel gear, but both of them can be used on the same axles. The long axle shaft allows you to change the track of the tractor within large limits, and the short axle shaft allows you to change the final drive ratio and driving characteristics of the tractor.
It should be noted that these axle shaft models are used on old and new models of MTZ tractors (Belarus), they were also installed in a similar UMZ-6 tractor.
The axle shafts are made of alloyed structural steels of grades 20HN3A and its analogues by machining of shaped bars or by hot forging.
MTZ axle shafts of the rear drive axle
The axle shafts take up space in the rear axle of the tractor, directly connecting to the driven final drive gear and to the wheel hubs. In old-style tractors, the additional axle shaft is connected to the differential locking mechanism.
The part has a simple design: it is a steel shaft of variable cross-section, on the inside of which one or two spline connections are made, and on the outside there is a seat for the installation of the wheel hub. The seat has a constant diameter along the entire length, on the one hand it has a groove for the hub key, and on the opposite side there is a toothed rack for the hub adjustment worm. This design allows not only to fix the hub on the axle shaft, but also to perform stepless adjustment of the track width of the rear wheels. In the central part of the axle shaft there is a thrust flange and a seat for the bearing, through which the part is centered and held in the sleeve of the axle shaft.
Currently, three types of rear axle shafts are used, their characteristics are presented in the table:
| Axle shaft cat.number 50-2407082-A of the old sample | Axle shaft cat.number 50-2407082-A1 of the old sample | Axle shaft cat.number 50-2407082-A-01 of a new sample | |
|---|---|---|---|
| Length | 975 mm | 930 mm | |
| The diameter of the shank under the hub | 75 mm | ||
| The diameter of the shank for landing in the driven gear of the final drive | 95 mm | ||
| Number of shank splines for landing in the final drive driven gear, Z | 20 | ||
| Diameter shank for mechanical differential lock | 68 mm | The shank is missing | |
| Number of shank splines for mechanical differential lock, Z | 14 | ||
It is easy to see that the axle shafts of the old and new models differ in one detail - the shank for the differential locking mechanism. In the old axle shafts, this shank is, so in their designation there is the number of teeth of both shanks - Z = 14/20. In the new axle shafts, this shank is no longer there, so the number of teeth is denoted as Z = 20. Old-style axle shafts can be used on tractors of early models - MTZ-50/52, 80/82 and 100/102. Parts of the new model are applicable for tractors of both old and new modifications of MTZ ("Belarus"). However, in some cases, it is quite acceptable to replace them without losing the functionality and characteristics of the transmission.
The rear axle shafts are made of structural alloy steels 40X, 35KHGSA and their analogues by machining or hot forging.
How to correctly select and replace the final drive shaft of MTZ
Both the front and rear axle shafts of MTZ tractors are subject to significant torsional loads, as well as shocks and wear of splines and gear teeth. And the rear axle shafts are additionally subjected to bending loads, since they bear the entire weight of the rear of the tractor. All this leads to wear and breakage of the axle shafts, which impairs the performance of the entire machine.
The most common problems of the front axle shafts are wear and destruction of the bevel gear teeth, wear of the bearing seat up to a diameter of less than 34.9 mm, cracks or breakage of the axle shaft. These malfunctions are manifested by specific noise from the PWM, the appearance of metal particles in the oil, and in some cases - jamming of the front wheels, etc. To perform repairs, special tools are required for pressing the axle shaft out of its housing, as well as for removing bearings from the axle shaft.
The most common problems of the rear axle shafts are damage to the slot, wear of the lock groove for the hub key and the rail for the adjustment worm, as well as various deformations and cracks. These malfunctions are manifested by the appearance of wheel play, the inability to perform reliable installation of the hub and track adjustment, as well as wheel vibrations while the tractor is moving. For diagnostics and repair, it is required to dismantle the wheel and hub casing, as well as press out the axle shaft using a puller. Work must be carried out in accordance with the tractor repair instructions.
For replacement, you should choose those types of axle shafts that are recommended by the tractor manufacturer, but it is quite acceptable to install parts of other catalog numbers. The axle shafts can be changed one at a time, but in some cases it makes sense to replace them with a pair at once, since the wear of the teeth and bearing seats on both axle shafts occurs with approximately the same intensity. When buying an axle shaft, bearings may need to be replaced and new sealing parts (cuffs) must be used. When replacing the rear axle shaft, it is recommended to use a new hub cotter pin and, if necessary, a worm - this will extend the life of the part.
With the correct selection and replacement of the final axle shaft of the MTZ, the tractor will work reliably and efficiently in any conditions.
Post time: Jul-26-2023