While servicing Range Rovers we have noticed a common problem of a blocked rear axle vent. Eventually, this can lead to seal failure and contamination of your rear brakes. The problem is in the banjo fitting at the rear axle. When you change the rear axle oil you hear a hiss of pressure released, or sense that the hypoid oil is being pushed out, then the vent is likely blocked. To clean it, remove the banjo bolt (as its name implied, it resembles the body of a banjo). Clean the bolt out and clear the hole in the banjo with a small wire. This simple maintenance step will save you from more serious problems.