I noticed the Moog links have a hex nut on the back side. The originals that were removed looked to have a back nut as well.

 

im hoping the dealer gets my sway bar in this week, i kind of hate driving my hhr lt1 with all this clankinking going on, its a 2010 with only 13000 miles on it...

 

I have a clunking, rattle in the front end, both sides, but louder on passenger side. Changed out to Moog end links, but noise still there.
Bought a Steadman electronic chassis ears[6 hookups], and checked everthing in the front end, and I mean everthing. Neighbors think I'm nuts[which they already knew] for driving around with wires hanging out and earphones on, up and down the street. Finally think I have narrowed it down to sway bar bushings, as thats where I'm picking up the most noise[noise in one place can travel to other parts, when they are hooked up to each other].
Ordered new bushings and caps for sway bar[should be in next week], and we'll see if it cures the problem.
Now, any noise that I hear, I can pinpoint where it's actually comning from.
Footnote: After I get this noise cured, I am going to put sound deafing from the firewall back, door panels, floor,the works. Going to quieten this noisy sucker down. "Moon'

 

I'm pretty sure the clunk I was experiencing was the bushings and I think over time (obviously 1-2 years) the Chinese rubber softens and allows the bar to move too much and contacts the frame or the bushing retainer which causes a very solid “clunk”.
Of course there are a half dozen parts in the front that can cause the clunk and there are also multiple levels of clunk (New thread anyone: Clunk definitions?)! In fact, if I really had to describe mine I would have called it a "Thunk".

Anyway, a broken or damaged strut will certainly cause handling and drivability problems, a bad axle shaft should (?) cause vibration or other sounds when shifting from reverse to drive or other drivability issues. The stabilizer and end links won't really cause any handling issues unless they are broken. They will still do their job as long as there is a solid-semi-solid connection between the two sides. The sway bar is mounted directly to the end links and to the K member via bushings in the front so if there is contact because of soft bushings there will be a very solid “Thunk”! So, if you have not noticed any adverse changes in the way the car drives or handles but just start hearing the “clunk”, bushings (<$10) are the cheapest and easiest start! If that doesn’t fix it move on to the end links!
I’ve been watching the thread about grease-able poly bushings. It will be interesting to see if any road harshness in transmitted to the frame then to the occupants using poly bushings.

Other Takes?

 

One of mine came apart while I was replacing it with Moog units, and I was thinking at the time, that I was glad it didn't happen while I was driving - it might be possible for a broken link to flail around and snag the brake lines, or cause other damage. Not a good design Chevy.

 

I replaced the endlinks with moog but the biggest improvement was replacing the sway bar bushings, no more noise and the car handles and feels a 100% better, on my HHR, the sway bar bushings were the cause of the clunk noise. I also replaced the outer tie rods (moog also) and now my steering is a lot tighter.

 

2006 LS HHR here with 45000 miles original.....aside from ignition key problems corrected by GM by changing steering and trans linkage....have had no major issues
just changed front stabilizer links due to increasing rumblings in front end....original GM links were dry and corroded when we removed them.....we replaced them with Moogs with zerts ..which we can lubricate when we do oil changes thereby prolonging their life