I think I need a little help from the experts. Today, while driving on the interstate, having been happily going along at around 80-85 mph for an hour or so, had to slow down to around 55 to 60 in heavy rain. At this speed, and it seems to be more pronounced while actually easing off the throttle, can hear a sort of rumble which appears to come from the rear of the car(or rather wagon). My wife thinks this only is audible when driving in rain, my theory is that I don't normally drive that slow unless it's raining!
Vehicle had it's 60K service about 6 weeks ago, and apart from this noise, everything seems to be AOK.
Any comments, please.