I recently brought my car in for an oil change. Once they got done, the guy at the shop said my rear axle pinion seal was leaking and recommended I get it replaced. He gave me an estimate for total cost (parts + labor) around $190. I've never heard of a pinion seal before, and don't know if that price is reasonable. Could any of you mechanic experts give me some advice on what the function of the seal is and what the typical cost to replace it should be? If it's something serious, I'd like to know so I can get it in to get it fixed. Thanks all!