RES4CUE

Wind buffeting as others have said. It's a difference between pressures in cab versus outside at certain speeds. On my scab it start around 45 mph and as I go faster it gets louder and more pronounced.

To solve it you need to crack another window.

Grandpa's Grocery Getter

Thanks everyone!!

It does seem to air pressure but its more of a,slapping sound..

Still to be determined...
I'll have to get someone to ride in the he back and check it out..or myself

Thanks for the comments

Grant