I have a rattling noise on cold starts when I go into gear. I am assuming it is a heat shield on the catalytic converter. After the engine is warmed up the noise goes away. I gave them a quick inspection & one side has the weld cracked but did not appear very loose. Where else can I look? Thanks.

RH

 

I have that same exact problem, it got noticeable after I removed my rear cats. All 3 crackhead muffler shops here want over $400 to replace the cats, so I'm most likely going to put LT's and high-flows.

 

Could be that heat shield, the way Fords heat shields clamp over is a bit of a flimsy design as compared to having them mounted on the cats permanently.