Haynes manual completely avoids any hints to tackle the auto gearbox on this model, stating that it is a sealed unit and any repairs "must" be entrusted to an approved specialist. All those approved specialists I contacted condemned this model on the grounds that gearbox problems were rife and even a new gearbox would most likely develop the same fault. I considered such remarks to be totally irresponsible. The claim is that the gearbox cannot be worked on or adjusted, that it is electronically controlled and sealed for life. This is misleading and not entirely true. The Service section in the Haynes manual details how to check the auto gearbox fluid level every 40,000 miles so good for reference. However, topping up did little to solve my problem.

My VW 2000 2.0 cabriolet Avantgarde 2d Auto was purchased second hand with approx 100K miles and little to no repair history provided.

The problem experienced was that the drive would grab (sometimes quite violently) and slip during drive. These symptoms became progressively worse. Most times the grab would be experienced from stand still and/or within seconds of drive off. You can imagine the potential dangers and fright when taking off from traffic lights or from a junction with either having no drive or losing it within moments of moving off. This problem reached the point where no drive was possible when starting off on an incline, no matter how slight. Strong instincts suggested that fluid pressure and/or valve movement was compromised.

Be aware that this fix (for me) was a time related process; meaning that the process is undertaken over a period of several weeks and I'll explain why.

A generic replacement filter, sump gasket (both come as a kit) and appropriate but reasonably cheap oil were purchased from a factor. Another quality filter was also purchased, together with a simple siphon pump and replacement gearbox filler cap securing clip (£1 from VW dealer). Haynes do not mention or walk you through this fairly easy service but do refer to the 40K service as mentioned for details on how to refill.

Chose a still, dry day since you don't want air-born grit to get on any exposed part of the gearbox during this process. With the car up and level on ramp and stands, the gearbox protective plate was removed (three bolts). Even if you do have an oil drip container or tray, place a makeshift frame on the ground (2 x 4 timbers laid lose) and lay some plastic sheeting over the frame to form a shallow pond that will catch spillage. There is no actual drain plug in the gearbox sump pan but what you think is a standard looking drain plug is actually fitted to an internal tube that act as the overflow when the fluid reaches the correct level during top-up. Remove the plug and note that only a small amount of fluid comes out. Slacken all the bolts to the gearbox sump pan and hold it in place when removing the bolts. Be prepared for hot fluid to pour everywhere but hopefully caught in your makeshift shallow lined framed pool. This is a potentially messy phase of the job. Note how the filter locates onto the underside of the exposed underside of the gearbox (it has a short protruding hollow tube that locates into the gearbox). It might still be attached but will come away easily. Have very clean hands if touching anything exposed and beware of the ribbon wiring and its connections. Discard the filter and gasket, thoroughly clean out the sump pan with integrated magnet. Oil will continue to drip from the exposed underside of the gearbox but by the time the bolts and pan have been thoroughly cleaned to spotless and the new gasket with spacers has been fitted, you should be okay to start reassembly. There is no need to wipe anything exposed on the gearbox except the flange rim where the sump pan seats. Soak the new filter with new oil and fill the sump pan. Locate the new soaked filter with the 'tube' up onto the gearbox and beware that it may drop easily. Have the bolts handy since it's tricky to offer up the filled sump pan whilst doing up the bolts to finger tightness and you might experience a bit of a spill so be forewarned. Tighten all the bolts to what I guessed at being about 9 lbs/ft or 12Nm.

Location of the filler plug is explained in the Haynes manual but it's situated just above the starter motor. It is possible to release the gearbox filler cap securing clip from around the filler plug but it requires pick tools and patience. Hardly worth the £1 cost of its replacement. Prise out the filler plug, start and keep the engine running on tick over until up to operating temperature. Keep the engine running as you top-up the fluid with the overflow plug removed from the sump pan. Press down on the brake and slowly engage all the drive and revers gears. Do this a few times. Oil flow might be slow but when oil starts to come out of the overflow in the sump, you've obviously put in enough oil. Replace overflow and filler plugs and bolt the gearbox underside protective plate back into situ. Lower the car and take it for a cautious drive. There might not be an immediate improvement but over the next week (or approx. 200 miles) it should drive better.

Only about half of the fluid was changed and it's now already contaminated with the other half of old fluid. One might argue that flushing oil could have been used but since you can't drain all the oil out in one go, don't be tempted to use flushing oil. Instead, repeat the dropping of the sump pan, cleaning and filling it back up again whilst using the almost new filter and gasket. Do this again the following week (or after another 200 miles approx.). There are no hard and fast rules about the number of times you do this or the duration between each drain and refill on but what you're aiming at is to end up with pretty much a clean oil in the end. I performed the task four times every other week because don't do that much mileage and ended up using 2 x 5 liters of oil. The second new filter and gasket was used on the last oil change.

The result is a perfectly smooth drive with no grabbing or slipping.