82 245 B21FT

This is really strange? When it really rains hard and there's standing water on the road/freeway, I get a really loud sound from either the motor or tranny ("I think")... It's like normal road noice but multiplied by 10... and it's not the water hiting the wheel wells... I'm thinking it's not the tranny but possibly from the motor. Maybe water is getting up into the belts or somethin but it's really loud... and it goes away after a little bit once i get out of the heavy rain and into the normal rainy conditions or dry pavement... This has only happened about 4 times in the two years that I have owned my 245... and it happenes when i'm driving in really heavy rain conditions and or driving through heavy puddles etc... Under normal driving conditions, the road noice is amplified a tiny bit between 50 and 60 mph but not nearly like the noice i explained above.. Just conserned and hoping someone here will have ideas on what it may be... If i can explain the noice properly, it is like a constant rumble or really loud fast vibration...

Thankyou
Svender