Knocking noise under car after bottoming out on driveway
Impact to the underside of a vehicle can bend or loosen protective shields, exhaust hangers, or suspension components like the CV axle and control arms. This creates persistent rattling over bumps and when braking, even if the car otherwise drives normally.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Checking components like swaybar end links, worn strut/shocks, inner tie rods, and link pinsDid this help you?
- 2Using a metal pipe under the control arm to lift and simulate going over a bump to locate the soundDid this help you?
- 3Replacing suspension components like sway bar linksDid this help you?
- 4Having mechanics inspect the vehicleDid this help you?
- 5Considering returning the vehicle's suspension closer to stock configurationDid this help you?
- 6continuing to driveDid this help you?
- 7inspecting for damageDid this help you?
- 8Moving hoses out of the way to check for rubbingDid this help you?
- 9Replacing engine mountsDid this help you?
- 10Considering replacing the belt tensioner or accessory pulleysDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“Been hearing knocking like the sound in the video when driving over bumps so I removed the wheel to investigate and this is what I found. Would you say that the CV axle needs to be replaced?”source ↗
“I backed my car up on an unfinished driveway and slammed my car on the ground and every since it does this knocking It drives 100% fine. It’s just a rattling sometimes it happens when I break I speed it’ll happen for almost anything.”source ↗
“Noise goes away when I accelerate or im at higher speed.”source ↗
“Does anyone know what this sound is? It only happens when I'm entering or exiting a ramp. I already replaced the sway bar links, but the noise is still there.”source ↗
“It's even been checked by mechanics and they still can't figure out where it's coming from—plus, all of this started right after I installed coilovers.”source ↗
“Also, it's been getting worse lately and happening more frequently.”source ↗
“I recently finished repairing the front end after an accident, and now I’m hearing this rhythmic “dun dun dun” / deep plastic tapping noise from the passenger side of the engine bay (serpentine belt area).”source ↗
Where this came up
People with this problem also raised
- 20Why does the strut top mounting plate rotate by hand?
- 2What to check after hitting a deep pothole or road dip
- 2Faint brake grinding noise after an alignment
- 32Why are my brakes squeaking and shaking the floorboard?
- 11How to tell if a front end shake is tie rods or wheel bearings
- 148How to explain an intermittent car noise to a mechanic