Before beginning repair of coupling, the transmission or mechanism of gear shifting if the cause of defect is unevident, then it is necessary to define their state and a possible cause of defect. Malfunctions of coupling and the mechanical transmission are determined by the complicated switching, in particular, the increased effort when switching, extraneous noise of tooth gearings, friction with a scratch or blocking. When any of these states it is revealed, the attentive analysis has to be carried out and the following checks and adjustments are executed.

Many noise which as it is supposed, proceed from the transmission can arise actually from other sources, such as tires, pavings, bearings of wheels, the engine or system of production of the fulfilled gases. These noise can change depending on the size of the car, type and amount of the applied insulating material of a body. Transmission gear wheels, like any mechanical devices, are not absolutely silent and will publish some normal working noise.

The following approach for check of suspicious extraneous noises of the transmission is offered.

1. Choose the smooth, evenly asphalted road to weaken the noise arising from tires and a body.

2. Pass rather long distance in the car thoroughly to warm all lubricants.

3. Write down the speed at which there is a noise, and transfer number of the transmission at this time.

4. Check noise at the movement and in the standing car with the working engine.

5. Establish at what of the following conditions there is a noise.

a. Transfer, intensive acceleration or the movement under loading.

b. The Bystry movement or preservation of constant speed of the car at insignificant loading of the engine on the flat road.

c. The movement on inertia with partially or completely closed butterfly valve and the included transfer.

d. All above-mentioned malfunctions.

6. After road check of the car address the table of possible malfunctions. Bearings of wheels make the noise reminding a rough roar or a scratch. This sound will be constant when the car moves by inertia and the transmission is in neutral situation. As bearings are installed without preliminary tightness, noise has to decrease significantly when wheels descend from soil.

Grinding in is caused by fine-grained particles of abrasive materials, such as scale, sand or sandpaper which circulate with oil and cause deleting of a roller and the surfaces of sliding. The erased bearings have a considerable side play, but their working surfaces are left smooth, without cracking or spots of corrosion that is result of oil pollution by nonmetallic inclusions.

Jamming of bearings is caused by the big particles of alien material putting between rollers and the surface of swing and usually forcing one of the surfaces of swing to rotate.

The preliminary tightness of roller bearings exceeding established can also cause jamming of bearings.

Emergence of sinks is result of normal wear which is shown in the form of corrosion spots on the surface of swing.

Emergence of sinks can also be a consequence of some adjusting or operating conditions as, for example, a gouging alien material.

Cracking is caused by an overload or the wrong installation. Bearings with cracks have or stratified, or corroded a rust rollers or the surfaces of swing. The wrong installation consists in the wrong adjustment, a distortion of bearings or their pulling.

Signs and the possible reasons of malfunctions are given in the table (Signs and the possible reasons of malfunctions of the transmission)