96 F150, 5.0L, auto, dual tanks. I think my front tank is filling my rear as when i'm driving on the front tank it appears that I am consuming a huge amount of gas. I switched to the rear this morning (empty a week ago) and it was now full. anyone know what causes this? i have read some other posts about check valves but they all appeared to be on older model F150's. i have a mechanical background but am very new to ford engineering, so any help would be great!