Volkswagens are the perfect cars to have when you want to stay comfortable on your commute around the Sound between Olympia and Seattle, tackle forest roads, or just enjoy a cruise along the Pacific coast. Transmission problems can take the fun out of your drive, but even if you can live with them, minor issues shouldn't be ignored: what may start out as some gear hunting or hard shifts can quickly turn into a failure that will keep your VW from moving. Here's what you should look for when trying to identify problems with your Volkswagen's gearbox, whether you have a manual, an automatic or a DSG.
When you push down on your VW's clutch pedal, you're moving a fork attached to the throwout bearing. This bearing carries the clutch and is mounted on the input shaft. Let go of the pedal, and the clutch slides forward, riding against the flywheel, which is attached to the engine's crankshaft. Power is transferred between the engine and transmission using this connection. The clutch is covered in a material that's similar to the lining used on brakes, helping it grip the flywheel. With each shift, a little of that material is scrubbed off.
Inside the transmission, the input shaft spins against the output shaft, and the output shaft spins the differential, which transfers power to the CV axles and finally the wheels. Both the input shaft and output shaft are covered in gears. When you move the shift lever, you're moving forks inside the transmission which push down on synchros. These synchros lock different gear sets to the shafts, changing the gear ratio.
German for “Direkt Schalt Getriebe,” this name literally means “Direct Shift Gearbox.“ A DSG works a lot like a manual transmission, except instead of a direct connection between the input and output shafts, the input shaft drives two shafts connected by clutches. One of these shafts is hollow and short, while the other one is long and sits inside the first shaft. The gears are split between these shafts, with one carrying the even gears and the other carrying the odd gears.
This separation allows two sets of gears to be locked at the same time. To shift up or down, the clutches engage and disengage, switching which geared shaft is connected to the input shaft. This allows for very fast shifts: once the gears change, servos can engage the next gear so it's ready when power shifts between shafts again. There's no need for a clutch between the engine and transmission, since both drive clutches can disengage for neutral. Since everything is electronically controlled, the transmission can also be set up to shift itself, just like an automatic transmission.
On an automatic transmission, power is transferred between the engine and transmission using a torque converter. Inside this donut-shaped device, fins on the input (engine) side spin around, moving fluid. In turn, this fluid movement pushes fins on the output (transmission) side, spinning the gears inside the transmission. The converter can “lock up“ at steady speeds, connecting the engine and transmission directly for increased efficiency.
The transmission itself uses planetary gearsets. Each gearset has a ring gear, which is round on the outside and has teeth on the inside. In the center, there's a sun gear, and between the sun and ring gears are several planetary gears. Each planetary gear is big enough that it spins against the sun and ring gears at the same time. Using clutch bands, the system can lock down one type of gear, letting the others spin around it. This changes the gear ratio. The valve body uses hydraulic pressure to engage and disengage these clutches. Old transmissions were strictly controlled by fluid pressure, using it to force open valves and engage clutches. Modern transmissions operate these valves using computer-controlled servos.
Volkswagen's Tiptronic transmissions let drivers control the servos directly, letting them control shifts. Aside from this electronic connection, they function exactly like any regular automatic transmission.
What Can Go Wrong with My Volkswagen's Transmission?
Over time, the synchros in a manual transmission will wear out. Normally, it takes a very long time for this to happen, but hard shifting can quickly take a toll on these components. In severe cases, the shift forks can be bent, preventing them from engaging the servos. Likewise, the clutch will wear out eventually even in the hands of the best driver, but poor technique can rapidly wear down the clutch surface, shorten its service life.
The most common problem with DSG transmissions is a failing temperature sensor. If the transmission control unit isn't getting the correct signal, it will have difficulties shifting, causing gears to slip and engage abruptly. Since the clutch and shift mechanism is electronically controlled, shifts are very gentle, resulting in a very long life span, but only if they're used with the correct transmission fluid. If an owner or technician uses the wrong fluid, such as a standard ATF or gear oil, it can shorten the life of the clutch significantly. Volkswagen has also changed fluid recommendations for some 7 speed DSGs due to electrical conductivity issues with the original synthetic fluid.
Automatics in Volkswagens are subject to the same problems as auto gearboxes in any car: clutch wear will eventually keep the transmission from holding a gear. Some transmissions have lifetime transmission fluid, but for older transmissions, ignoring maintenance will shorten the life of the internal components. Running the transmission without enough fluid will burn out the clutches, causing the transmission to fail. In VW transmissions, hard downshifts are usually caused by failing control modules. If left unrepaired long enough, these abrupt shifts can damage the transmission.
Getting Parts for Your Volkswagen's Transmission
When you need to fix your car's transmission, do it right the first time with Original Equipment Manufacturer (OEM) parts. These parts are built by VW specifically for your vehicle, so they fit and function just like the parts used when your car was constructed, and they've backed by a warranty from the automaker. Where's the best place to get OEM parts? www.OEMVolkswagenParts.US. Our site lets you search for parts based on your model and VIN as well as part numbers and descriptions like “solenoid” and “DSG.” Need to know more about a part or application? We have a staff of factory-trained parts people who can answer your questions.