Oil on the rear wheel and rim of a Ford Transit - halfshaft oil seal leak

An oily wheel rim, a wet brake disc or drum on the inner side, and gear oil dripping from the lower edge of the wheel are typical signs of a leaking halfshaft oil seal on a RWD Transit. An important diagnostic rule repeated on owners' forums is that the seal rarely fails by itself. It is usually damaged by play in the hub bearing, so replacing the seal without checking the bearing often results in another leak after a few thousand kilometres. A halfshaft oil leak is also a safety fault: gear oil contaminates the brake shoes or pads and dramatically increases braking distance. Contaminated friction linings must be replaced; degreasing does not restore their performance. On early MK6 models, also check halfshaft end float, as some vehicles were covered by a recall for this issue.