VW DSG (direct shift gear transmission) and Audi S-tronic FAQ
VW DSG (direct shift gear transmission) and Audi S-tronic FAQIntroduction
This article discusses the basic pro/cons of the DSG, how a DSG works, and common problem areas with the DSG. S-tronic is Audi's name for DSG.
At the bottom are some review videos of the DSG. To differentiate between the DSG and a conventional planetary gear-torque converter automatic transmission, I'll call the conventional auto a slushbox. Tiptronic is a term used by VW and Audi and only refers to a non-manual transmission that lets you shift the gears with the shifter. Below is a cutaway showing the manual transmission type gears and dual clutch system of the DSG. Make sure to also read page 2 of the DSG-Stronic FAQ for more technical pictures, how it works, and videos.
Summary of DSG operation
VW's direct shift gearbox (DSG) is a 6 speed dual clutch manual-like transmission that automatically shifts. It has internals similar to a manual transmission with a "brain/valve body" called mechatronics which shifts it. Depending on the model, VW/Audi and Borg Warner currently make DSG transmissions. It's better than a conventional automatic transmission and great on turbo cars because the more consistent power delivery keeps the turbo spooled up. The main disadvantage vs. traditional manual transmission is that it's harder to modify and heavier. The fluid and filter should be changed every 40,000 miles. (also see How to change your DSG or S-tronic fluid) As of 2011, VW Auto Group has made around 3.5 million DSG transmissions. Almost all are made in Kassel, Germany with a few made in Dalian, China.
The DSG was first introduced to the US in 2003 with the model year 2004 New Beetle TDI and Audi TT. The gasoline NB still used a slushbox for that year. 5th generation VW Jetta TDI starting in 2005.5 also got DSG. Premium trim cars equipped with slushboxes had a rolling change to DSG across the VW model line over the years. If the car is premium trim, it should have a DSG. Base cars usually still come with a slushbox.
Steering wheel paddle shifters for TDI with DSG were introduced in 2010 but you can retrofit them to earlier 5th generation cars and new 6th generation cars, see 1000q: paddle shifter steering wheel retrofit for more details. The stock gear selector looks like a normal automatic gear selector with "park, drive, sport, etc." and a tiptronic position. All DSG cars should have a DSG badge on the gear selector. Pictured below is an example from a 2004 New Beetle highlighting the badge. The gear selector has PRND positions just like an auto slushbox. S is sport mode and the +/- position is the tiptronic position. Both DSG and slushbox may have the tiptronic position.
Some have said that the DSG transmission learns your driving style but this is technically incorrect. The DSG transmission shift behavior adapts to variables like internal wear, D or S mode, and other input factors like throttle position and rate of change, uphill or downhill, and applies these variables over an existing shift map. Learning is the wrong term since it means new knowledge that wasn't there before- the transmission cannot learn anything new, it just applies variables to existing maps. Some engineer has already determined and tested how the shift maps and variables will react. There is no single input field "driving style". The perception of a reaction to driving style is the result of the change in a number of variables applied to the shift maps. So yes the transmission adapts but not how most people think. Although "learn" might be used in marketing literature, it's not the right word to use when describing technical operation.
This article focuses on the 6 speed DSG found in North America but there are also 7 speed DSG for front wheel drive (transverse layout) and longitudinal DSG for rear wheel drive.. The 7 speed transverse DSG isn't available in North America because it's limited to 184 lb-ft of torque and we don't have the low output engines. The biggest difference in the 7 speed is the extra gear and the dry clutch vs a wet clutch. More gears and the dry clutch should give greater performance and fuel economy but dry clutches aren't cooled by fluid and could have limits on launch mode. The torque limit means it won't appear on US TDI engines anytime soon. In any case, TDI have such a wide torque band that a 6 speed DSG is more than sufficient to work very well.
Here is a video showing how the Porsche PDK (Porsche Doppel Kupplungen, Porsche double klutch) dual clutch transmission works. Even though ZF and Porsche developed PDK independently from the Borg Warner developed DSG / S-tronic, the video explanation works for both. There are also dual clutch shift type transmissions from Mitsubishi (made by Getrag) with other manufacturers following.
Pros and cons of the DSG
A DSG is a great transmission compared to a slushbox. If you leave it in automatic mode, it's identical in ease of use. It's lighter and has less parasitic power loss. You should also notice faster shifting and better fuel economy than a slushbox. A DSG can also deliver better car performance and smoother shifting than a manual transmission. In fact, the newest generation of high performance sport cars are faster when equipped with dual clutch transmissions, everything else being equal. Since the mechanism never misses a shift and the clutches are almost always engaged, DSG give more consistent power delivery, especially in turbo cars. In a manual transmission turbo car, you normally lift off the throttle during shifts to rev match the engine, interrupting power delivery. Because a DSG only has a tiny gap in power delivery, the engine is kept under load which keeps the turbo spooled up. The DSG also eliminates driver inconsistency in performance shifting.
A DSG is also good for drivers with knee problems or family members who don't want a manual (or you can't stand their shifting)! There are some some quirks with a DSG and these are discussed in further detail below.
Despite these advantages, I still feel that a manual transmission is better for a skilled driver who doesn't mind shifting. If nothing else, a manual transmission gives the driver the ability to maximize the fuel economy which is one of the strongest points of a TDI. It also costs less and is more tolerant of higher level power upgrades or poor maintenance. A DSG needs consistent fluid changes every 40,000 miles. See this FAQ article on how to do this 1000q: DSG DIY fluid change. Conventional manual transmission gear oil can go anywhere between 60-100,000 under normal use. Many independent garages and even some dealerships are not experienced with the service requirements of the DSG because it's still relatively new. A DSG will also not let you rev to engine redline because it will force a shift slightly below redline.
Some other disadvantages of a DSG are potentially lower reliability, higher replacement costs, and heavier weight compared to a manual. In theory, the DSG on the TDI should give better performance but the increased weight and greater parasitic power loss take away performance compared to a manual. The clutches in a DSG are lubricated in fluid and this creates greater parasitic losses than a dry clutch. So far, the real world difference in performance between manual and DSG (when mated to the VW/Audi 4 cylinder gas/diesel engines) isn't statistically significant and is well within variations in driver, environment, tires, and engines.
Power upgrades and the DSG
While the DSG's official limit is 258 lb-ft (350 nm) of torque, it's possible for the transmission to hold more power. Stock torque on a TDI engine is 170-236 lb-ft, depending on the engine. HPA motorsports built some high power testers for VW and they experienced no unusual problems. They recommend fluid changes every 10,000 miles on high power modified cars. And of course, how much you actually use that available power and towing/racing use will effect transmission and fluid longevity. If you have a TDI, the ECU has a torque limiter so that any power upgrades will not go over the DSG limit. To gain the full benefit of power upgrades you may need a DSG tune.
If you want huge power gains, you may also need a new clutch pack. While a conventional manual transmission clutch can be changed without too much difficulty, there aren't too many places to find and install DSG clutches.
The new 7 speed DSG used on the Audi S5 can hold up to 406 lb-ft but it's used with a longitudinal engine, not the transaxle used on the 4 cylinder TDI. The new 7 speed DSG on the Euro Golf/plus is for small output engines and is limited to 184 lb-ft.
DSG transmission reliability and common problems
A DSG transmission is a great piece of technology but it's still relatively new compare to a manual transmission. Because of this, a factory extended warranty could cover any potential problems that won't show up until some miles and age have accumulated on the car. I would rather put aside a general emergency fund for home/auto/health repairs, but it's an option. Just carefully read what an extended warranty covers and terms because the contracts are often worded to exclude many repairs, certain "wear parts", or exclude items which don't have a strict maintenance history!
Below are some of the more common problems reported. If you do report a drivability or safety problem to the dealer, some will tell you to keep driving it because the part is on backorder. If the car has a drivability or safety issue, demand a loaner car or rental car and file a report with the NHTSA. Driving an unsafe or defective car is unwise and this can be a dealer trick to avoid lemon law criteria in some states.
Recent update: VW has extended the warranty on all DSG or S-tronic transmission for 10 years/100,000 miles, transferable to subsequent owners for 2006-2009 model years. This covers the R32, Jetta, GTI, Eos, and Audi TT and A3 and only applies to a "limited production range", whatever that means. It's unrelated to the recall mentioned below. To see if your past repair or current car is covered you have to call the VW loyalty center at 1-800-444-8982. A .pdf copy of the warranty extension for DSG transmission letter that was sent to owners is below.
DSG NHTSA investigation
The National highway transportation safety administration (NHTSA) recently opened an investigation on power loss and jerky power delivery of the DSG. While the number of DSG with problems is small, the problems reported which opened the investigation are serious and could result in a crash. This investigation is not limited to TDI, it's for all VW/Audi DSG. The NHTSA action number is PE09035 opened July 17, 2009 and currently covers 2008-2009 models.
While some DSG have a small delay in clutch engagement and power delivery from a full stop, this is considered normal and can be expected and compensated for by the driver. The more serious problems involve false neutrals for no reason, shifting into neutral by itself, and not being able to shift back into drive from neutral while at speed. These sorts of problems are not unique to DSG transmissions or VW since they can occur on any car with a defective part or faulty design. However, there are many more anecdotal problems reported than just the cases which resulted in the opening of the investigation. Ultimately, the opening of an investigation means only that there are problems reported which merit further investigation and this should currently be the only conclusion which one should draw from this action.
Temp sensor recall
On Aug 2009, VW started a recall on 2009 and 2010 DSG on the temperature sensor. Models affected are built between August and September 2009. A faulty temperature sensor can result in illuminated warning lamps in the dashboard and the transmission may shift into neutral. It appears that both sensors below are in the same assembly. This is probably responsible for some of the flashing "PRNDS shift light" incidents. Below are some descriptions of the temperature and rpm sensor.
A low battery (also check voltage regulator or alternator) can cause flashing PRND or PRNDS lights and DSG shifting problems. If you get the blinking shifter PRND PRNDS light and false neutrals (transmission shifts into neutral by itself) then you could have a bad transmission temperature sensor as mentioned above. Here is an example of a stuck neutral on a 2009 Jetta TDI and a similar problem on a 2007 Audi A3.
Other common issues showing up are DMF or mechatronics problems.
Mechatronics houses all but 2 sensors in the DSG transmission and all external input signals for controlling the transmission go to it. There are also pressure control valves and solenoids that control shifting. The individual parts are not yet serviceable separately. It's designed to be replaced as a unit and the retail price is in the thousands of dollars! A brand new DSG transmission costs about $5,500! Used transmissions from an auto recycler are currently the only economical option. So far, there have been over 1 million DSG units made so the price should go down over time. Here is a video showing removal of mechatronics. It's in German but you can figure out what's happening.
Please continue to page 2 of the DSG - S-tronic FAQ for more technical pictures, details, and reviews.