Whenever I press on the gas there was a rattling coming from or what I think is under the car but I am not 100% sure I just got a muffler put on three days ago and the sound did not exist before then.
My car has 96000 miles.
My car has an automatic transmission.
Loud metallic rattles are not uncommon as vehicles age. That the noise did not start until some exhaust repairs leads to the same spot. An exhaust heat shield. Some exhaust components have a heat shield welded to them. In other instances, the heat shield is bolted to the underside of the vehicle. These heat shields can be two-piece construction, like a clam shell. They are spot-welded is several locations. From age these spot welds can rust and break. The two pieces of the shield will then rattle together. Sometimes constantly and other times, only in certain gears or rpms. It may not necessarily be due to anything other than age and the parts being moved to install new components. Take it back to whoever installed the exhaust system and ask them to take a look underneath.
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