I know, this is an old thread but I have the same issue. If the truck sits level with about 3/4 of a tank of gas, it leaks. If I park on a hill (front higher than back) the gas stops leaking. When the tank reaches 1/2 full, no leak at all. Is it a seam or the fill neck? I can't locate a new tank so anyone know where to get one or, how to fix a leak on the old one? If it's the filler neck, I can fix it. Thanks.