The clunk many of us hear coming from the rear of the car after installing aftermarket rear sway bars appears to be the combination of three things:

1) The polyurethane bushings provided with most all aftermarket sway bars
2) The "sticky" grease provided in the kits
3) The OEM endlinks

First off, everyone says the problem comes from worn OEM endlinks. This doesn't appear to be true. Here's why. If my endlinks were worn, then why is it that when I've regreased the bushings trying to fix this problem, the clunk went away for about 2 to 4 days? The endlinks can't magically repair themselves. The sound you're hearing DOES come from the endlinks, but it's not because they're worn. When you mount up an aftermarket sway bar with tight fitting poly bushings and grease them with the provided sticky waterproof grease, the bar is very resistant to move in the bushings. The bushings require a lot of force to rotate the bar up and down (endlinks unattached). I'd venture to say that when bar is mounted and the bushings/mounts are torqued to spec, it probably takes over 80lbs of force to get the bar to initially rotate in the bushing. I'm a pretty strong guy, work out often, and it takes me a very healthy tug to get the bar to move downwards. With the OEM rubber bushings, it takes maybe 5lbs. I could make that bar move with my fingers.

When you initially do the aftermarket bar install, you've greased up the bushings nicely across the whole face of the bushing. You drive around for the first few days and there's no noise or clunk. Then as the days go on and the grease works it way off the outer edges of the bushing, which are smooth and in 100% direct contact with the bar, the bar starts to become very resistant to move in the bushing. This lack of movement or response in the bushing, as well as the force needed to move the bar, requires the endlinks to have to work overtime to lift up/push down the bar. Not only is the bar a lever to resist roll in the chassis, but the bar must be able to move up and down through the range of suspension travel. At slow speeds, usually under braking and on almost smooth surfaces, you start to hear this "clunk clunk". The clunk is most definitely coming from within the endlink itself as it tries to move the bar up and down slightly. The bar is slow to respond so something inside the endlink pops and the sound is transmitted to and through the bar because the endlinks have direct metal to metal connection. At higher speeds and on larger bumps, the suspension movement up and down helps the endlinks do their job hence the reason you rarely hear the clunking under these situations. Using aftermarket endlinks will most likely get rid of the clunk because the endlinks are far beefier and apparently can handle the lack of bar movement caused by the bushings.

The other and far cheaper option to a $150-170 set of endlinks is to grease the bushing with slicker and lighter weight grease and modify the bushing so that the bar can move easily. The fix is super simple.

The fix:

1) Remove the bar and remove the poly bushings. Clean the grease off the bushing.
2) Take a Dremel with the sanding wheel and grind out the inner portion of the bushing. Make sure to hit all areas of the bushing. Don't grind out a whole lot. About all you need to grind out is 1mm, maybe a little more.
3) Test fit the bushing and bar back on the car and test to see if the bar is easier to move once mounted and torque to spec. If it's still tight, remove and grind out a little more. The key is to go little by little because there's no going back.
4) Once the bar moves freely, regrease the bushing and remount everything.


I did this fix about 10 days ago and the clunking is gone.

 

Good write up and it makes sense. Do you have pics of "the fix"?

 

I thought about taking pictures, but during the process I realized the pictures wouldn't be benefical because all they'd show is a bushing covered in poly shavings. Basically all you're doing to expanding the inside of the bushing. When the unmodified bushing is on the bar, it moves freely, but once the bushing is in the collar and torqued to the chassis, it gets very very tight. After a few days of driving, the bushing gets even tighter as the grease gets worked out.

 

This is very helpful. Thanks for posting. What about putting a spacer/washer on the bolts for the mounts so that it does not clamp down on the bushings as strongly? (if I am understanding this correctly)

 

I considered it and it may work, but was a little worried about collar sliding around on the washer under extreme loads. I also feared a potential shear issue since I don't understand the loads on the bolts. I'd hate to know what it takes to fix one of those bolts if they shear off. So, I thought it would be better to modify an $8 bushing instead

 

Prudent reasoning - thanks.

 

Good stuff!
I actually have some squeeking noises coming from the rear at low speeds (parking lot, speed bumps, etc.) after I installed Hotchkis TVS, which I thought was worn endlink(s). I'll look into brushings now.

 

Good info. Bring this thread back to life. I'm going to get some zerk fittings and install them on the front sway. I'll test to see how much force is needed to move the sway after being tight on their for over a year.

 

Yeah, My fronts squeak pretty bad when I accel even mildly. Thing is, they were installed recently and packed w/grease. The clunk is not present just the squeaks

 

My fix was a lot simpler. When re-installing the sway, make sure you put force against the mounting bracket to force it outward against the collar on the sway bar. Do that on both sides and the swaybar won't have space to move back and forth and won't make clunking noises.

The fix for clicking endlinks is to make sure they are tight enough on the swaybar. Most aftermarket sways appear to have a slightly larger hole drilled through them leaving too much room around the stud out of your endlink. If you don't tighten it enough, it has a little play in the hole so you'll hear a slight click from the front end when you go over bumps, etc.