Mystery "Thunk"

[LakeDave]

I have 2019 Mustang Bullitt. I track it 2-3 times a year, just to drive fast, I'm not competitive. I've installed Vorschlag plates just to save some tire life. Also running 285/35 ZR19 square set up. Those are the only changes I've made. Now the car has a frustrating, "thunk" sound when I drive over rr tracks, pot holes etc. It's a 'heavy' thunk, big metal, not a light metal sound. Seems like the thunk is front left wheel, or now maybe front under the driver dash location? You have to drive it over rr track or bump at 10-15 mph to make thunk sound. At first I thought is was driver side, shock/vorschlag set up. Took it out made sure all was tight and reinstalled. Still the mystery THUNK is there. Now sounds maybe under driver side dash??!! I don't have lift. I've jacked up car, look around, tapped some parts with rubber mallet What's loose? The car drives fine, no problems. I'm guessing a bolt with two big metal parts needs tightening. Car has only 15,000 miles. I had alignment (-2 deg each front tire for track) and they said it wasn't ball joints. Anybody have any ideas or hints before I take it to the dealership? Thank you.

 

[PatientZero]

Have you verified your front sway bar end links are both bolted up and tightened down?

 

[mwjscn]

The Vorshlag units use spherical bushings for an all-metal connection between the shock shaft, the caster/camber plate, and your strut tower which will induce more noise into the body than the OEM rubber bushing isolators, especially going over railroad tracks and potholes. You probably hear it more in the driver's side because that's where you're sitting. Not to say there couldn't also be something loose, but increased noise is expected when using spherical bushings where there used to be soft OEM rubber. It was noticeable to me when I made the change over, but you get accustomed to it over time.

 

[DaveW]

Have you verified your front sway bar end links are both bolted up and tightened down?

This X11million. At least 9 times out of 10, maybe 99/100, when a customer car presents with a clunk, it is a loose end link. They basically need to be tightened as tight as you can get them with a standard length wrench/ratchet. Ignore any factory torque specs.

DaveW