Hello, I know very little about cars, so please be gentle. I have a 99 Subaru Outback Wagon with 195,000 miles. Lately, when I make turns, particularly while accelerating, I hear a knocking sound in the front left side, near my feet. The mechanic can't find anything, but I have heard other people suggest my axle may be bad. Can anyone give me a rough estimate at what it would cost to fix it?