First post here--hopefully somebody out there can help as I'm automotively challenged.
I've noticed that occassionally when it rains (heavy), I get a loud knocking sound that seems to come from under the car, roughly under the center console. This happens only at low (under 30 mph) speeds. I can actually feel the knocking vibration on the center console. This sound comes and goes. I've never experienced it when it's dry and only occassionally when its VERY wet.
The car has 82,000 miles, is well maintained, and has hi-test (91 octane) in the tank.
What do you think it is? Is it safe to drive? (My wife just called me, she drove two hours on the highway, and as soon as she got on back roads she called me and said the car is making this noise. I am assuming she's hearing the same thing I've occassionally heard in the past.
All replies appreciated. Thanks in advance.