Expert advice: Dsg & S-Tronic Mechatronic failures


Expert advice: Dsg & S-Tronic Mechatronic failures

Volkswagen DSG gearbox Vw dsg gearbox Volkswagen dsg gearbox

If you are a VW or Audi owner then you are familiar with the two names DSG and S-Tronic.  Both these transmissions have made a name for themselves in the last 8 to maybe 10 years. They are super smooth and changes gears extremely fast. In fact so fast that some reckon they are faster than a very good driver in a manual gearbox vehicle.

But what are they exactly and are they really any  good?  Some say its an automatic and some say its manual.  Some even say its the best of both worlds.

Whats the difference?

Which is better? Dsg or S-Tronic?  Well the answer might surprise some. Neither one is better than the other. In fact, they are the same.  These gearboxes is used in different guises by both the Audi and Vw groups and some of their other partners.  Basically its only the names that changes for the different brands.

Both these transmissions are known for their smooth shifting and fast reaction times.  They are also called “thinking gearboxes” because they always seem to know what the driver intends to do.  In short, they do not differ that much if any.

What is a Dual clutch transmission?

A dual-clutch transmission (DCT), or Direct- shift transmission (DSG) (sometimes referred to as a twin-clutch transmission or doubleclutch transmission) is essentially a type of automated manual transmission in vehicles. They are closely related to a manual transmission and uses two separate clutches for odd and even gear sets. It combines the convenience of an automatic with the efficiency of a manual transmission.

Audi refers to these transmissions as S-Tronic but essentially they are the same.

How does it work?

The Dsg & S-Tronic gearboxes uses two clutches, but has no clutch pedal. Sophisticated electronics (mechatronics unit) and hydraulics control the clutches. In a dual clutch gearbox the clutches operate independently. One clutch controls the odd gears (first, third, fifth and reverse), while the other controls the even gears (second, fourth and sixth). Using this arrangement, gears can be changed without interrupting the power flow from the engine to the transmission.

Common problems.

Although these are great gearboxes, some of them can develop some problems. Overall they are very dependable but we have seen them more than once in our Vag Spec workshops where customers have been given the wrong advice and wrong diagnostics done on them.  Lets have a look at some common problems.

  • Incorrect solenoid operation in the computer and periodic errors during diagnostic. More than one sensor can get faulty, and getting the data from them will be impossible. Electronic components on the main board may get damaged, and errors can appear on the software program of the gear change control due to incorrect data.
  • Temperature sensor failure – either failing outright or failing out of specification. Incorrect data will cause the computer to do what it thinks is right based on the data it receives; hence, failure results. When this happens, certain gears stop working, either at a time or all at once. You may notice grinding or bad fuel economy.
  • The most common problem on the valve body is usually the appearance of gaps between the valve seat and the valve under normal wear. The presence of elements that are not part of the composition of the transmission fluid can lead to rapid wear. Failures in the mechatronic unit can also result due to a problem in the automatic transmission in general.

Until the problem is fixed, the mechatronic unit will continue to break down. Proper diagnostic and maintenance are very crucial.

What is the Mechatronic unit?

A mechatronic unit is the control centre of the gearbox. It is found in the gearbox where we have the direct-shift gear oil (DSG). Its task is to manage the torque converter and the clutch pad of the gearbox via the transmission fluid under specific pressure. It is capable of performing shift operations in a second. The gearbox’s control unit is in constant communication with the engine control unit, and this helps to determine the right time when changing gear.

Simply put, the mechatronic unit is a computerised control part of the dual-clutch system. This unique advanced dual-clutch automatic transmission is found in many cars, but mostly Audis and Volkswagens. The dual-clutch transmission consists of two sub gearboxes, each with its clutch, that work together to shift the gear.

The electronic control unit is made up of sensors and valves (actuators) in one single component with the main function of opening one clutch and closing the other at the right moment. This results in smooth shifting without any interruption of the tractive force. The unit processes the sensor signal, operates the valves, measures the RPMs, and slides of the hydraulic gear mechanism.

The mechatronic unit evaluates the selection of data. From the data, it recognises whether the gearbox needs to change from first to second gear, for example.

What happens when they fail?

The challenge with these highly advanced transmissions is that at some stage something is bound to go wrong.  When things do go south, you need expert advice.  These days its not just any mechanic that can work on your vehicle anymore.

But what are the warning signs?  Here’s the most common signs of a mechatronic unit starting to make trouble:

  • Clonking in gears
  • Selector warning lights
  • Inability to select gears
  • “PRNDS” lights flashing
  • Gearbox keeps selecting the neutral position

When this happens its best to stop driving and speak to your local technician first.  Its not all doom and gloom though. In days gone by it was only your local Audi and Vw dealership who could repair these sophisticated pieces of engineering. These days there are specialist repair centres who can do even a better job of repairing the transmission. In fact, dealerships these days will quote on replacement of the whole gearbox and maybe if you lucky only the mechatronics unit.

Vag Spec Centres have become well known through out South Africa as experts on all Vw group vehicles as well as BMW, Mercedes, Mini, SEAT, Porche and more. The group specialises in the diagnostic and repair services for DSG and STRONIC transmissions. They pride themselves in excellent and honest customer service and will go the extra mile to get you back on the road with expert advice, the latest equipment and years of experience between all their qualified technicians.

Visit our Vag Spec Centre branches here for expert advice on all transmission related enquiries:

VagSpec Centre Zeerust

VagSpec Centre Randburg

VagSpec Centre Nelspruit

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