when I am on the Interstate, say at 70mph, I get like a random clanging banging noise under the car - but I pulled over and all parts of the exhaust system seem in great shape and the car runs and handles great.
my theory is that perhaps some gravel may have gotten up inside a heat shield in the exhaust system and the high speed wind in causing turbulence and rattling these rocks around - does that sound likely? - other theories?
how many heat shields are there that I need to disassemble and check? - anyone had this happen before?
Does your have the main lower engine cover still on? Any cracks on it and especially around where the mount bolts go?
There are also two side covers where the strut mounts are, check those. The rest of the covers don't get as much turbulent air as the front ones do. Otherwise some suspension bushing is definitely unhappy at that rate of speed so there is metal on metal contact. If you drive over a rough surfaced road at lower speeds does it occur?
and the noise seems to be coming from the underside of the car, at least halfway or all the way to the back, like at the rear wheels area - I see some shields near the tires that would be the right place.