How to Repair an Automatic Gearbox?

Automatic gearboxes are becoming more and more common and are no longer something exclusive to the most expensive brands and high-end cars and are now used in all types of vehicles. This, added to the high cost of this transmission, has meant that knowing how to repair an automatic gearbox in mechanical workshops is an operation that is carried out with increasing frequency.

gearbox repair

The transmission is one of the most expensive and complex systems of a vehicle, which is why in the mechanical workshops, once the vehicle is out of warranty; offer their customers the possibility of resorting to an alternative to the replacement of the component.

In order to save in this sense, and sometimes ruling out changing the component for a second-hand one that comes from a scrap yard that can present similar problems, there is the possibility of opting for automatic gearbox repair.

Possible failures of a gearbox

The latest generation models offer features that make the cars themselves; have a protection mode that comes into operation at the moment they detect a fault in the transmission system. In this way, it is about preventing the initial fault from being more serious.

Before proceeding to disassemble the transmission to replace or repair it; The professional will have to carry out an exhaustive diagnosis of the breakdown in order to determine if the fault is inside the gearbox or if it is an external problem.

Some of the breakdowns that occur most frequently and that make it necessary to repair or replace the automatic gearbox are the following:

  • Breakage of the drum in which the gears are housed or that of the transmission input shaft. You can guess that you have this problem if you notice difficulties when changing gear and jerking in the vehicle.
  • Fault in the torque converter. There are oil leaks in the car’s transmission and a great vibration will be appreciated when the vehicle is idled.
  • Worn clutch discs or gear group. It is a fault that will cause the vehicle to take too long to change gear or even not to do so because the change “slips”. It is usual that the ATF liquid is not in the right conditions, causing friction between the metal parts that make up the transmission.
  • Oil pump failure. It is a breakdown that can lead to knowing how to repair an automatic gearbox or its replacement. It can cause damage similar to that which can occur if degraded ATF fluid is generated. At one point it could prevent the vehicle from responding completely.
  • Control unit failure or valve body failure. If this type of fault occurs, the vehicle’s response will not be adequate when changing gear. Usually there will be a knock and in these situations it is not necessary to disassemble or repair the gearbox, since the fault is external to it.

How to repair an automatic gearbox?

The process that must be followed if you want to know how to repair an automatic gearbox is the opening of its three main blocks; which are the gearbox, the torque converter (in the models that are equipped with it) and the electrohydraulic unit (valve body). The three groups must be completely disassembled to make the corresponding diagnosis of each part.

When a gearbox is repaired, it is necessary to replace all the components that are in a situation of continuous wear, such as the filters; segments; Clutch plates; seals; boards; bushings; gears; washers…; and that when replacing them, you opt for other high-quality components.

Those elements that can be preserved must be cleaned so that they are freed of possible impurities that may have accumulated. Once the repair of the gearbox has been completed, it is important to make the corresponding assembly of the three components mentioned above, respecting at all times the adjustments, tightening torques and gauges indicated by the manufacturer.

When the box has been assembled and closed, it must go through a test bench; and make use of a hydraulic and pneumatic tester to check the pressures and operation of the automatic gearbox; as well as doing the same with the valve body and the converter. If after carrying out all the checks everything works perfectly, it will be time to reassemble the transmission in the vehicle; fill it with the ATF oil indicated by each manufacturer; and carry out the basic adjustments that are required to readapt it.