'06 Pathy with a Rumble noise

[Pathfinder7]

Let me start by saying I too am a victim of the faulty Transmission Cooler. It leaked in to my transmission and $3,000 later I am not happy. I am out of warranty so I went to a shop I found on Angie's List. They diagnosed the coolant in the transmission and recommended a Transmission overhaul, new Radiator and upper and lower hoses. While it was in I had them do spark plugs and Fuel system cleaning. I told the Manager about a noise I was hearing at 40 MPH up through 70MPH. The way I explained it was it sounded like I was driving over Rumble Strips.

Has anyone successfully diagnosed and fixed a problem that sounds like this? The shop I was had looked at everything (so they said) and could not find the problem. I was hoping it was in the transmission and the O/H would fix. The found the Drive shaft out of balance, but that did not cure the problem.