The Haldex clutch engages the rear axle when the front wheels slip. The pre-charge pump blocks up with oil sludge, and the rear axle simply gets no drive: the car appears to run faultlessly as long as grip is good. The telltale sign is the front wheels spinning while the rears stand still. The same unit sits in the Tiguan I and the Passat B8 4Motion. The fourth generation Haldex, built up to October 2013, has a replaceable filter; the fifth generation after it does not, and there the oil change is the maintenance. Prevention is cheap, the consequence is not: replacing a neglected unit is a major expense.
What to check
- Ask when the Haldex oil and filter were last changed: if never, budget for it immediately
- Check whether the car is 4Motion at all: the presence of a rear differential is visible under the car
- On a loose, gravel or grass surface pull away firmly: if only the front wheels spin, that is suspect