Manual gearboxes – why (most often) break down?

Manual transmissions, used in the vast majority of vehicles, are relatively durable and do not cause major problems, functioning properly throughout their lifetime. However, emerging problems mainly result from improper operation, including excessive overloading of cars and lack of transmission oil level control. One of the most common faults is excessive wear of the bearings in the gearbox, which can lead to serious damage.


The most popular manual transmission installed in modern cars is made of two shafts: the clutch, the main one and the intermediate one (in some solutions two intermediate shafts are used). A gear wheel is mounted on the clutch shaft, which transmits the drive to the intermediate shaft wheel. On both shafts there are pairs of gears corresponding to individual gear ratios: engaging a certain gear disconnects the other wheels. In addition, in vehicles with front-wheel drive, there is also a differential in the gearbox housing, commonly known as a differential.


Probably many vehicle owners would be frightened by the characteristic sound of loud howling or noise coming from around the gearbox. Most often it is heard in a certain gear ratio and increases with increasing rotational speed. This is the most common symptom of gearbox bearing damage. It should not be underestimated, because prolonged driving with a damaged bearing often leads to the destruction of the gears.

There can be many reasons for excessive bearing wear. The fault may result, e.g., from prolonged use with maximum load or from a lack of control of the transmission oil level. To make matters worse, in some car models the bearings wear prematurely (due to gear design errors, among others). An example of such an unlucky nanual is, for example, the M32 box, which can be found in Opel and Fiat.
However, not only bearings can be the cause of too loud gear operation. Noise audible only on one specific gear ratio may suggest that the gear has been damaged. However, if during switching individual gears there are difficulties with their proper selection or – what is worse – we hear disturbing grinding sounds, then it can be concluded that the synchronizers have been damaged.

Regardless of the symptoms of incorrect transmission operation, the final and correct diagnosis can be made only after dismantling it. The detection of a defect is particularly important because damage or excessive wear of one part causes in many cases the failure of the other. Therefore, after dismantling the crate, a thorough examination of all its elements is carried out to exclude the risk of secondary failures. TEAM

Audi maniac, owner of and big fan of Audi cars. Maps, firmware, car audio installer
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