FAQ Automatic Transmissions

Is my transmission damaged?

As soon as automatic transmission problems become known, we recommend to act immediatley. Often, it is still possible to repair minor damages before serious problems occur.

For technically competent vehicle owners, it is recommended to check  the transmission oil. The transmission dipstick needs to be pulled to check the transmission oil. The oil level is checked through the overflow pipe at max. 35 ° - 40 ° C, the manufacturer's instructions needs to befollowed.

Furthermore, the oil pan can be removed to screen the oil pan and the filter for contamination.
If the transmission fluid is not burned (original colour: red or yellow) and no shavings can be found in the transmission oil, there is a real chance that the transmission is not or not badly damaged.

In mechanical-hydraulic transmission likely causes for malfunctions are: defective vacuum units, a defective kickdown, a hanging governor, a defective sliding shift housing or transmission oil shortage.

In more recent,  electronically controlled transmissions, however, an external error can be responsible for failures. Examples are: a faulty throttle position sensor, a defective control computer, a damagaed mass air flow sensor or harness.

Further possible causes are: faulty switch or pressure control valves, speed - pressure - or temperature sensor as well as sliding shift housing and lack of oil.

If your vehicle has no forward nor backward drive, often, it seems likely that the torque converter is defective.

What is the difference between a repair and a general overhaul?


In case of minor transmission defects, we carry out targeted repairs on a time and material basis. We repair only the obviously defective parts that need to be replaced. Fahrzeugtechnik Hetzel gives half a year warranty on the parts replaced.


Complete Overhaul:

In a general overhaul, the automatic transmission is completely disassembled and thoroughly cleaned. Thereafter, a fault diagnosis is performed. Defective parts will be replaced. The individual components are carefully checked and assembled.

The torque converter is either replaced or repaired. The valvebody or the mechatronic is tested on a special test rigs slide switch for function and performance. Afterwards, all modules are reassembled into a functional transmission. The transmission is checked on one of our transmission test stands before delivery.

The overhaul is carried out at a fixed price, unless the transmission housing is damaged. Fahrzeugtechnik Hetzel provides a warranty of 12 months with unlimited mileage during these 12 months.

All critical parts are exchanged, regardless of whether these parts are still functional or not.


In a nutshell:



Complete Overhaul



Obviously defective parts are changed

(only possible if the contamination level is not too high)




All wear parts are exchanged. The single modules are tested and installed.





Price on a time and material basis



Overhaul flat rate



Torque Converter can possibly used again



Torque Converter is changed / remanufactured everytime.



Warranty covers the changed parts only



1 year warranty without mileage limitation for the whole transmission *.



On a time and material basis.


The transmission is disassembled and thoroughly cleaned. Afterwards a fault diagnosis is performed.




On a time and material basis.


The Valve Body / The Mechatronic is tested on special test stands to check the performance and the function.




*There is only a 6 month warranty for commercially used vehicles.

Why is it necessary to replace a functional torque converter when a transmission is overhauled?

Almost always defective automatic transmissions are heavily contaminated. Then dirt particles such as metallic shavings or burnt clutch linings, are located in the torque converter.

If the old torque converter is used again, all the dirt gets back in the transmission via the oil circuit. This will damage the transmission again.Rinsing of the torque converter is not sufficient enough to remove all dirt particles. It is not possible to look into converters with a lock-up clutch, therefore it is unclear if the friction lining or the lock-up clutch is damaged already.

Only transmissions that do not have a high degree of contemination can be repaired at all. In this case, for cost reasons, the torque converter may be used again.

Why does the the oil cooler need to be cleaned or replaced?

Shavings or a burnt clutch lining may be transported through the oil circuit in the oil cooler.
If the transmission is overhauled but the oil cooler is not cleaned thoroughly, the dirt particles get back into the transmission via the oil circulation. In some cases, the oil cooler is so dirty that no adequate or no oil flow at all is possible. Then a sufficient transmission oil cooling is no longer guaranteed.
In such a case, or if huge shaving in the transmission are present, the transmission oil cooler must always be replaced, otherwise the overhauled gearbox will overheat and be damaged again within a short time.

Is it possible to repair a transmission when it is still installed?

The transmission has to be removed definetely, when the transmission oil is dark discoloured (brown or black), or when it smells burnt. If this is not the case, the oil pan should be removed and screened for metallic abrasion. Heavy metal abrasion and rather large shavings on the magnet are indicators of serious mechanical damages. In this case, a strong mechanical defect is quite likely and the problem cannot be solved in the installed state.

Is there a collection service available?

We work with a forwarding company to pick up and deliver transmissions. We charge a flat rate nationwide from 60, - € + VAT (per way and transmissions up to 100kg). Transmissions should be packed as compact as possible on a small pallet e.g. in a box. The oil needs to be drained and the transmission must be packed spill-proof so no oil can leak during delivery. All shipping documents need to be completed. A simple delivery note with your letterhead and if possible, a short description of the problems and placing orders is sufficient. Of course a request of information can be attached. As soon as we know your desired 

Can the forwarding company take the old transmission at the same time it delivers the exchange transmission?

Experience has shown that the best way to compare both transmissions is to put them directly next to each other prior the installation of the replacement transmission. In this way it can be determined if all attachments are unscrewed from the old transmission. For that reason we recommend to send the old transmission at a later date to us.
In addition, most forwarding companies deliver in the morning and pick up during the afternoon.

Any further questions? Please contact us.

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