In trucks, the rear axle gearbox is the most loaded mechanism. This is due to its design features and the functions assigned to it. It is strictly forbidden to operate a truck with a faulty rear gearbox. Usually this ends with a node failure, sudden breakdowns, and high repair costs. To avoid such problems, it is enough to pay attention to typical signs of a gearbox malfunction and eliminate the causes of their occurrence in a timely manner. You should also not ignore the scheduled maintenance provided by the manufacturer.

Why do you need a rear gearbox on a truck?

In order for freight transport to be used for its intended purpose, it is not enough to equip it with an engine and gearbox. The transmission must contain a gearbox, to which:

  1. Transmits torque boosted by the gearbox from the engine to the drive wheels.
  2. Reduces the angular speed of rotation of the drive shafts.
  3. Increases traction on the drive wheels.
  4. Ensures the independence of the wheelset.
  5. Allows you to block the drive wheels to overcome difficult areas.
  6. Transmits force from the drive wheels to the motor in engine braking mode.
  7. Changes the rotation vector, allowing the transmission of torque to drive wheels that are not aligned with the cardan shaft.

Mechanical gearbox - mechanical transmission of energy by rotation, converting the speed and torque in magnitude. Based on the etymology of the term, derived from lat. reducere "reduce", the main function of the gearbox is to reduce the force required to drive a device that converts mechanical energy into useful work.

The traditional type of mechanical gearbox is a gear train in which the drive gear is smaller and the driven gear is larger.

Rear axle - a unit of a wheeled or tracked vehicle that connects the rear wheels of one axle. It is attached to the frame with a suspension.

The main function of the rear axle gearbox is to transmit and increase torque.

Features of the rear axle gearbox

The development of the rear axle gearbox is carried out in order to solve the following problems:

  1. Ability to perform assigned functions.
  2. The presence of a margin of safety sufficient to overcome extreme loads.
  3. Minimization of the mass of the mechanism, which positively affects the dynamic characteristics and fuel consumption.
  4. Reduction of friction forces between parts, which reduces fuel consumption, increases dynamic characteristics, and increases the resource.
  5. The gearbox must be serviceable and maintainable.

The main indicator of the quality of the rear gearbox of a truck is strength. When designing, it is taken into account that the entire load falls on only three pairs of teeth of the final drive.

The rear gearbox of any truck is a technically complex multi-component mechanism. It typically consists of:

  • main couple;
  • shank;
  • bearings;
  • glands;
  • dirt rings;
  • corps;
  • differential;
  • semiaxes.

The complexity of the gearbox device significantly complicates the diagnosis and repair. Additional difficulties arise due to the huge mass of the node. Rear axle maintenance ultimately requires special equipment and tools.

Why is it forbidden to operate with a defective gearbox?

The operation of a truck with signs of a malfunction of the rear gearbox is not provided for by engineers. With slight wear, the car can drive more than a dozen kilometers. However, if the fault is further ignored, it will always end up in serious problems.

Possible consequences:

  1. Accelerated wear of resource-intensive parts.
  2. Mechanism failure.
  3. Bridge jamming.
  4. Increased fuel consumption.
  5. Decreased dynamics.
  6. Expensive repair.
  7. Penalties due to the disruption of the transportation of important goods.

In order not to encounter these consequences, it is necessary to identify and eliminate malfunctions of the rear gearbox in a timely manner.

The main breakdowns and their signs

Most typical breakdowns can be diagnosed without the help of service specialists on certain grounds.

Typical malfunctions

Typical truck rear gear failures include:

  1. Wear of the main pair.
  2. Bearing failure.
  3. Loosening the shank nut.
  4. Oil leak.
  5. Incorrect adjustment.

Other breakdowns are associated with the design features of the unit on trucks of certain brands, series, and modifications.


You can determine the listed typical malfunctions of the rear gearbox of a truck by the corresponding characteristic features:

  1. Critical wear of the gears of the main pair. Indicates an increasing howl as the truck accelerates. If the howl disappears after releasing the gas pedal, then this is a clear sign of wear on the main pair. With a certain degree of wear, the hum may disappear at a stable full load. When driving, the noise disappears.
  2. Bearing wear. Constant monotonous buzzing of the gearbox in the speed range from 20 to 80 km/h. At higher speeds, the hum is dampened by aerodynamic noise. In fact, it does not disappear, but simply ceases to be audible. The symptom manifests itself in all modes - under load, when coasting, engine braking.
  3. Spontaneous loosening of the shank mounting nut. It leads to its dangling, which can be determined with tactile diagnostics. The defect can cause extraneous knocking noise during movement, as well as cause noticeable vibrations.
  4. Oil leak. It is determined visually during an external examination of the node. It leads to overheating and accelerated wear of the rubbing parts of the mechanism.
  5. Incorrect adjustment. It manifests itself in the form of extraneous noise after replacing the gearbox. If there was no noise, and then it suddenly appeared, then it most likely indicates one of the previous malfunctions.

Adjustment of the rear gearbox is carried out once - when installing the assembly. Scheduled periodic adjustment is not required.

Truck gearbox maintenance frequency

Scheduled maintenance of the rear gearbox of a truck consists of two stages:

  1. Visual inspection.
  2. Change of oil.

Inspection is carried out before each exit from the garage. During the inspection, oil leaks and mechanical damage are detected. The oil is changed according to the regulations developed by the manufacturer of a particular truck. This usually needs to be done every 3 years or 300,000 kilometers.

On the maintenance of passenger cars on site ABS.