The powertrain is one of the most precise car systems. In addition, it is comprised of elements whose replacement is very costly, such as the gearbox, the clutch, the half-shafts, and - in the case of a four-wheel drive - the camshaft and the differential. Diagnosing its failure is often time-consuming and complicated, the more so that most of the systems are controlled electronically. The most frequent failures of the powertrain include damage to the gearbox, wear of the clutch elements, failure of the drive joints, play in bearings and the camshaft support. All powertrain repairs should be performed by professional mechanics.