Last evening, I was working on a used ATV I bought and when I changed the rear gearcase oil, about 6-8oz of water came out first, then a heavy black oil. I realize this is not right and it needs to be completely drained and replaced with proper oil. But my question is, where could water enter the rear gearcase from? Any help is appreciated.

Matt

 

First place to check is the rubber vent hose at the top of the gear case. Trace it from beginning to end looking carefully for holes or tears. If its damaged pick up some oil resistant hose from you dealer or auto parts store and replace it in one length. Its such a small size that hose joiners can affect airflow and breathability, plus a spliced hose is a possible future leak.

 

Thanks for the reply.

I was wondering what the small hose was that led to many of the components on my ATV. Does this just provide air to the component?

 

It lets it breathe, as the gearcase heats up from riding, the oil and air in the gearcase expands. If there were no vent the pressure would build to the point where oil was forced past the seals. The vent prevents this.