DSG gearbox tips
Made popular by the Volkswagen group, the compact DSG (Direct Shift Gearbox, or Direktschaltgetriebe) was the first twin-clutch transmission to be released on mainstream sale from 2003. Other carmakers have developed their own versions, in collaboration with transmission specialists, so we shall call ‘DSG’ “Twin Clutch Transmissions”. Pictured is Ford/Volvo’s version, called Powershift – click on the image for a larger view of the components. Regardless of manufacturer, Twin Clutch Transmissions have not been entirely trouble-free but our Technical Advisor comments that you can extend the length of this transmission greatly, by heeding the following 10 tips.
1. Adjust your driving technique. Most people were sold Twin Clutch Transmission cars as ‘automatics’. They are more correctly described as ‘automated manuals’ – a subtle, but important difference. If you are interested, look-up how the gearbox works and be aware that certain driving practices that do not harm conventional torque-converter transmissions, such as holding the car still using the throttle, can shorten a DSG transmission’s life markedly.
2. Know wet from dry. One of the main issues involves the clutch plates (or their bearing surfaces) wearing out. More powerful cars are equipped with wet clutches, which are situated inside the gearbox and are lubricated by oil, meaning that they have a very long service life. Dry clutches tend to be fitted to lower powered engines (typically below 2.0-litres) and, generally, do not last as long, especially if the car tows heavy weights. As they are more efficient, dry Twin Clutch Transmissions are becoming more popular on the latest cars. Changing a dry clutch unit is very tricky and bespoke training is required.
3. Change the oil. The pressurised oil, within the Twin Clutch Transmission, is under immense stress, especially on units fitted with wet clutches. Most carmakers insist that the oil and the external transmission filter are changed at specific intervals, typically, every 40,000 miles. If you do not have proof that this work has been done correctly, your warranty will be invalidated – see Tip 10.
4. Change your anti-freeze. Many Twin Clutch Transmissions shed the heat from the gearbox, using the engine’s cooling system. While anti-freeze possesses anti-corrosion properties, they tend to wear out and last for between 5-7 years. If you neglect engine coolant changes, there is a risk (especially on 6-speed VW DSG units) of the heat exchanger corroding and anti-freeze glycol entering the transmission, which destroys the internal parts. It is also vital to use anti-freeze of the correct type – Volkswagen Group cars are very sensitive in this regard.
5. Maintain the car’s cooling system. As the Twin Clutch transmission needs to shed heat, the car’s cooling system must be kept in impeccable order. Most notably, replace the radiator, even if it looks only slightly corroded, and be wary if the engine starts to run hotter than normal. Most Twin Clutch Transmissions will shut down, if their oil temperature exceeds a nominal 140 degrees Celsius.
6. Replace your battery in good time. If your battery is dying, it may still start your engine but the momentary low voltage that results, as it tries to turn over the engine, can cause a spike in the Twin Clutch Transmission’s Electronic Control Unit and damage the software. Fortunately, some specialists can open-up the sealed ECU and repair it. However, on many types, the ECU is part of the Mechatronics unit, which is a combined hydraulic and electronic block that is located within the transmission (see picture) and significant dismantling is required to retrieve it. For similar reasons, never jump-start a Twin Clutch Transmission-equipped car using another vehicle.
7. Listen for strange noises. Speak to a transmission specialist, if you hear anything out of the ordinary. For example, rear input shaft bearing failure is common on the 6-speed Volkswagen DSG units that, if left unchecked, can cause further expensive damage. Twin Clutch Transmission cars also use conventional Dual Mass Flywheels, failure of which tends to be indicated by a ratting/jangling noise to be heard. If left unchecked, the flywheel can disintegrate and may damage the gearbox casing irreparably. Crunching, especially on VW DSGs in the lower gears, tends to be caused by failing synchromesh, which is of a different type than that used for the higher ratios.
8. Look for low pressure issues (clutch slip) – As the transmission relies on hydraulic pressure to apply clamping forces on the clutches, a reduction in pressure can cause slippage and result in excessive clutch wear and, possibly, the oil overheating as well. The common symptom of judder, when moving off from a standstill on VW 6-speed DSGs, tends to be caused by an internal pressure leak and dismantling the gearbox to replace the internal gaskets is the only cure.
9. Be wary of bodges – Seek transmission specialist advice, if you are considering modifications to increase the internal pressures, which is common to stop clutch slippage if the engine’s performance has been increased. You could end up shortening the transmission’s life. Some companies advocate using an engine oil seal stop-leak additive to stop internal pressure leaks, or external seepage. Unfortunately, these fluids swell all of the seals indiscriminately within the transmission, including those of the pistons, which will impede their operation.
10. Scrutinise your warranty – Check your car manufacturer’s gearbox warranty very carefully. If you have a used car warranty, or have taken out a separate mechanical failure insurance policy, scrutinise the small print to verify that the transmission and its clutches are included. You may have to provide evidence that a potential transmission failure was not down to owner neglect and so ensure that the correct fluid and quality filters were used at all specified oil changes.
Finally, be aware of manufacturer goodwill. GEM’s Technical Service was involved in a case of DSG transmission failure a few years ago, when a member contacted us with Twin Clutch Transmission failure, seven years old 2.0-litre VW Golf that had 80,000 miles recorded. We found that engine anti-freeze had entered the transmission and the case concluded with Volkswagen UK backing 70% of a complete DSG gearbox replacement, leaving the owner with a £1,000 contribution. The main reason, cited by Volkswagen UK for its goodwill decision, was that the car in question possessed full main dealership service history. Therefore, buying a used car with full franchised dealer service history, even one from an auction hall, may give some safeguards, if there is a suspicion about the health of the Twin Clutch Transmission.