Patrol 4×4 – Nissan Patrol Forum

Maintenance after Water-crossings So once you have successfully crossed to the other side and are on your way home, you don't need to give the water crossing a second thought, right? Wrong! Any crossing at axle depth or deeper necessitates a checking of the diff oil for water contamination. Having an extended diff breather is not a 100% guarantee of waterproofness and any crossing above your axles without extended diff breathers should mean a mandatory inspection. Checking your diffs for water contamination is very easy. Since water is heavier than oil, it will collect at the lowest point in the diff, right where the drain plug is located. After allowing time for your 4x4 to cool, just loosen the drain bolt and run a small amount (~20mls) of the diff oil into a glass. If you're unlucky enough to have water present, the diff oil should be drained. It is best to flush the diff several times to ensure all traces of water are removed. Milky colored oil also indicates water is present and should also be changed.