Debugging front suspension dull knock

[silverlock]

Chasing a dull knock under vertical travel that I noticed when parked. Bouncing the fender or bouncing on the passenger sill with moderate force exhibits it. Photos and video link below.

Current theory: top strut nut is not holding the strut down. I can rotate the nut with moderate force on a wrench, whereas the drivers side is tight-tight. Attempting to tighten it causes the spherical bushing to spin as I can’t get purchase on the strut shaft.

Should I keep attempting to thread the nut down? Risk of damaging? Open to ideas here. The adjustment knob (tab) on the Koni’s doesn’t give me anywhere to get some grips wrapped in a rag or similar to hold the strut shaft.



Video link: https://www.dropbox.com/scl/fi/fvfpfw4otwzv0jsij9xm8/Video-Nov-16-2025-13-19-32.mov?rlkey=54lzstx8g02e6zjh1fo0mgqao&st=9khas7d4&dl=0

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Everything (yes, everything) on this car has been progressively replaced in the last 2 1/4 years. Shocks & t-bars are ~13k miles old. Sway bars & tie rods 17k miles. ER spherical a-arm bushings 10k miles ago. Tarret camber plates 10k miles ago. All bushings are < 2 years && > 6 months old.

What I’ve checked alongside this:

* removed everything from the frunk (including the jack)
* checked the bumper (pushing it up/down)
* checked the fuel tank clamps
* 3x a arm bolts good (witness marks on almost everything too). Hadn’t moved.
* 1x rear a-arm bolt good.
* 1x sway bar end link good.
* 1x top oil cooler 13mm good
* 2x bottom oil cooler 13mm good
* 2x horns good / horns not knocking on anything
* Cooler fan 12V harness zip tied to the horns for good measure.
* 3x Camber plate socket heads good
* Shook the cooler hard for good measure.
* Wheel bearings OK (no knock/play when shaking wheel hard)
* Skid plate tight

Alternate hypothesis is the gland nut that holds the strut down has backed off a tad, but that seems unlikely. Would need to pull the strut + remove the dust cover to do that.

[A930Rocket]

The nylock portion of the nut looks like it has very little purchase on the threads. Maybe change it for another nut, to see if you can get it tight.

I know it’s frowned upon, but I tighten the strut top nuts with a battery powered impact. I don’t whale on it, I just get it tight.

[PeteKz]

Impact driver will do the trick. Just be sensible and stop when it bottoms. I use a Milwuakee 1/4” impact driver to make sure I don't over torque it. It’s not a loose gland nut.

[silverlock]

Thanks both: was wary about using the impact but a few blips at low RPM on the 1/2” works for me!

Also realized I don’t have a 1/2” 22mm socket in my kit so picking one up today and will report back. Grabbed some fresh M14 nylocks for good measure.

[A930Rocket]

Is the silver object under the nut one or two piece? If it’s two piece, you might want to takeoff the smaller top piece to get more thread engagement

[silverlock]

Originally Posted by A930Rocket

Is the silver object under the nut one or two piece? If it’s two piece, you might want to takeoff the smaller top piece to get more thread engagement

One piece. It’s the bushing for the monoball as part of the Tarrett camber plate.

The knocking is new, the camber plates have been on the car for 10k miles now.

[silverlock]

Update: no dice. A few careful ugga duggas and no change in noise when bouncing the front right. Fully removed the nut for good measure, and no material change in sound there either.

From a couple of side chats we’re now wondering if it’s the control/a-arms moving in the RSR bushings a little, or the lower ball joint.

The front end of the RSR bushings looks good left vs. right wrt spacing between the a-arm "ear" and the rear of the bushing (about ~2mm each side) and the bolts haven’t backed out. Witness marks there were checked in the first pass and everything is tight-tight. The tow hooks have taken a beating, so there’s a small but non-zero chance it’s put the a-arm out of alignment in the bushing?

Going to jack the front up and see if anything has shifted…

[Otter74]

Are you sure it's the strut upper mount? A loose bolt holding the steering rack shield / anti-roll bar mount can cause a very similar symptom.

[EC900]

Had similar front right knock though maybe not a pronounced, also thought about strut being loose when bouncing the fender, there was some knock noticeable on turns at slow speed and even some tire squeal on full slow speed turns in parking lot so thinking ball joint.
All front suspension was tight on jack stands. Routine wiggling the tire and found bearing was very loose, maybe 1 to 1-1/2” turn loose. Didn’t notice any bearing damage or spindle scoring, repacked bearing(s), tightened the nut to spec and noise was gone.

[Locker537]

Grab the A-arm and try to push/pull it parallel to the car. Those spherical bushings can have some play front to back.

If it's that, loosen the 3 bolts on the front of A-arm, push it rearward, re-tighten.

[Jim2]

When bouncing your car in the video place your other fingers tips between the red anodized strut perch and the lowest washer, see if you can detect movement, then the top washer and nut....

Mono ball outer race may be floating in the perch or, the ball race could be smoked. These are typically kevlar lined races in order to have zero slop and stop that sort of noise and subsequent pounding out the races.

[silverlock]

Originally Posted by Otter74

Are you sure it's the strut upper mount? A loose bolt holding the steering rack shield / anti-roll bar mount can cause a very similar symptom.

Definitely not 100%. Just the least confident about it. I can’t get the top nut as tight as the drivers side: I can snug it down so that it’s (far) more than finger tight, but putting a wrench and moderate force still allows it to turn. The drivers side cannot/does not tighten down any further under the same force.

Going to also check the:

* a-arm fore-aft play in the spherical bushings.
* double check the wheel bearing (no obvious slop/play, but doesn’t hurt to check again with more force)
* ultimately get it to the shop so we can pull the strut insert and inspect it as well.

For posterity I went over every bolt & nut again. Skid plate. Sway bar bracket bolts. Tie rod ends. Sway bar ends. Lower strut bolt. Nothing backed out or with obvious play.

[Otter74]

By the look of that photo, it might could just be a bad shock.

[PeteKz]

Given that the liquid traces are on the outside of the shock cover, and not the lower body of the shock, I'm pretty sure that was from spraying penetrating oil or some lubricant on the top of the shock to help tighten the nut.

[silverlock]

That’s why I didn’t mention it: if the shock insert was bad and leaking from the shaft seal I’d expect to see it on the strut. No traces of any fluid/oil there.

[silverlock]

Originally Posted by Locker537

Grab the A-arm and try to push/pull it parallel to the car. Those spherical bushings can have some play front to back.

If it's that, loosen the 3 bolts on the front of A-arm, push it rearward, re-tighten.

Before I do this tomorrow: jack just the one side up? Both sides to unload the arms?

Need to put jack stands under the a-arms if I jack both sides up, so assuming that isn’t necessary / conflicts with adjusting the a-arms.

[PeteKz]

I would jack up both sides. Otherwise, the sway bar will be putting a lot of force on the A-arms, and may limit the movement so you can't find it by wiggling them.

[Locker537]

Originally Posted by silverlock

Before I do this tomorrow: jack just the one side up? Both sides to unload the arms?

Need to put jack stands under the a-arms if I jack both sides up, so assuming that isn’t necessary / conflicts with adjusting the a-arms.

Jack up the front.

I use a piece of 2x4 with a jack on the front cross member between those tow hooks. Place the jack stands on the corner of the tub inboard of the front wheels. Safe. If you are worried about cosmetic damage on the tub from the stands, use different style stands (like the ESCO) or some more blocks of wood.

You want the a-arms dangling free. Push/pull parallel to the car.

When you check the wheel bearing, don't be surprised if you feel play in the strut. At full droop, that is quite common.