So I've had this annoying rattle when I have the AC on, truck in D, and foot on break. Slipping into N it goes away. Sounds like it's coming from the backend. But now I hear it AND a metallic rattle/clanking. I'm assuming it's transmission related? Any ideas where to look?

 

rattling heat shields on exhaust? A/C will give different idle/vibration frequency than normal, so that's my guess.

 

Exhaust heat shield.

 

Agreed. You can find an extra large stainless steel hose clamp at Home Depot that will fit everything but the muffler. Put a couple of them on and the rattle will go away. they will be in the HVAC/Plumbing dept.

 

Thank you! I am on it.