I hit a dead dear and soon after started feeling and hearing loud banging or knocking sound from beneath the car specially in middle of car, mainly does it after like 10 minutes of driving or almost hitting 2,000 RPM, but not all the time. what could it be, took it to a shop but they didn't find anything.

EDIT: Video of the noise.

2017 Nissan Altima SR 2.5 L

  • Welcome to Motor Vehicle Maintenance & Repair! Could you please include what kind of vehicle you are talking about? Year/Make/Model/Engine Nov 5, 2022 at 19:39
  • Perhaps the exhaust system was damaged and is now hitting the frame or body.
    – jwh20
    Nov 6, 2022 at 1:06
  • Random knocking, or regular knocking like a component that is rotating?
    – HandyHowie
    Nov 6, 2022 at 8:24
  • it's a random knock, doesn't do it every time, but when it does its hard
    – Edgardo
    Nov 6, 2022 at 15:01

2 Answers 2


Look for a loose plastic panel somewhere under the vehicle. If the fasteners that hold the front edge of the panel have been ripped out, the panel can randomly catch air and start banging around until you slow down. The banging only happens after you exceed some threshold speed. To repair, replace the fasteners, possibly with extra large washers to cover any area damaged by ripping the fasteners out.

  • @Edgardo Also check the air dam, if you have one, and any plastic body parts down low on the front end to see if they are loose. Any of those can act the same as the loose plastic panel that I mentioned above. Literally flapping in the breeze.
    – MTA
    Nov 6, 2022 at 15:35

This sounds like the wheel arch liner splash guard also known as mud guard. The plastic rivet seems to be knocked out, making the guard loose and hit on the wheel when driving due to air, but when hoisted they take the normal position, that would explain why the couldnt find the issue.

I would check if you have missing plastic rivets there

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