[tobster1911]

Originally posted by legion
I'm taking it to a mechanic tomorrow morning. I called the shop a relative takes his Ford truck to for work. He seemed to think it's a main bearing on the crankshaft.

If so, it looks like I'm buying a new truck while I'm in Florida. The cost of a bottom-end rebuild exceeds the value of the truck.

I've been checking the oil at every stop. The oil is new and clear, there is plenty of it, and there are no oil leaks.

And why would filling the gas tank have any effect on this? Sounds fishy to me. Did they offer to buy the truck off you cheap? If it was a spun bearing, why would the pressure drop?