I have a 2000 f-150 5.4 liter v8 and for the last month it has been making a loud noise like it has no muffler on it. This only happens when I am in drive and for about the 1st 30 seconds of it driving. It doesn't happen if I rev the engine in neutral. And it goes away and sounds all normal and performs normaly. Could anyone tell me what this could be?

Lee

You could possibly have exhaust manifold leak. The noise goes away after it warms up and the metal expands enough to seal it possibly.