I found the rattle in my Jeep. A few months ago it was recalled for the catalytic converter. To remove that they had to do it from underneath and Jeeps have a rock guard that protects the oil pan. It has about 7 bolts holding it on and is a heavy piece of steel about 2' wide.
The Jiboni's in Jeep left off at least 4 bolts and broke one in the hole so it has to be drilled out.
They are a weird metric size almost a 7/16th SAE bolt but not quite. I have a lot of Metric bolts but not that one and being it's Memorial Day, Jeep isn't open.
Tomorrow I will go back to Jeep to get some of those bolts. I don't want them to "fix" it because I don't trust them.
If they give me a hard time and want me to leave the vehicle with them, I will just go to a hardware store and buy the stupid bolts. This is a pain to fix because besides leaving off 4 bolts, the thing is on slightly crooked so some of the holes don't line up so I have to loosten all the bolts and drill out the broken one and use an "easy out" on it. I am to old for this nonsense but broke one of my rules by letting them work on my car.
The thing was recalled so it was free but nothing in life is free and if you want something done correctly, you need to do it yourself.