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Old 07-08-2012, 09:32 PM   #1
DiscoStu
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Arrow Lateral Swaybar Movement?

I'm looking for some help diagnosing this rear end clunk, or popping, sound. I feel I'm pretty good at diagnosing issues with this car, but this one has me wondering. For starters, I have H&R swaybars. They are about 4-5 years old and have roughly 50k miles on them. A couple of months back my car developed a clunking noise from the rear when making low speed, sharp turns to the left and right. The clunking can also be felt, meaning I can feel it when sitting in my driver's seat. The performance of the suspension does not appear to be compromised. The noise came immediately after I replaced the end links with new OEM. The previous end links were also OEM.

Thinking perhaps the noise was completely coincidentally to replacing the end links, I also replaced the outer lower and upper rear control arm bushings/ball joints with brand new ball joints. Also replaced within the past year are the RTABs and all seven subframe/differential bushings.

I'm stumped. What I'm thinking is that my swaybar has lateral movement. It seems to begin holding tension during a turn, then shifts, which is causing the pop. It also seems to be just as bad regardless of what stiffness I have the swaybars set at. Has anyone ever had this issue before? Is it even possible? Unfortunately, I'm having a heck of a time sourcing new H&R swaybar bushings, so I can't just replace those to see if it's the cause. The H&R swaybar bushings I have now are lined with teflon and feel worn to the touch.

Anyone have any thoughts? Thanks!
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Old 07-08-2012, 09:54 PM   #2
fiveightandten
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Do you see evidence of the bar moving laterally? If you can't see it in the grease or paint on the bar, wrap twist ties (like, from a loaf of bread) around the sway bar right where it meets the bushings. Drive the car around and see if they're pushed from the bar shifting.

Does it happen more than once, or just a single clunk as you change direction? When does it seem to 'reset' itself and happen again?

It's tough to say without knowing a little more about what makes it happen. I'm honestly a little doubtful that the bar moving laterally would exhibit a big clunk like you're describing. For that, you probably have some sort of tension loading up and unloading forcefully. Unless the bar is moving enough to get caught on something (you would see evidence of this if you looked around), i'd be looking at other options.

Have you looked long and hard at the subframe mounting points? Also, check the RTAB carrier. Get a screwdriver in between the carrier and the unibody and pry gently while you look for movement. I wouldn't rule out the diff, or even a CV joint either (does it repeat with wheel speed ever?). Drive around in tight circles and listen carefully for any grinding noises. Have a friend walk alongslide the car or you walk alongside it while it's moving to see what can be heard.
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Old 07-08-2012, 10:04 PM   #3
DiscoStu
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Thanks for the twist-tie idea. I may actually give that a try. I'm having a hard time telling if there is lateral movement by just looking for markings near the mounts.

This is a single clunk when I change direction. It'll clunk once during the turn and won't happen again until I turn the opposite direction. The 'reset' is when I turn the opposite direction. I can make a turn, straighten out the car, then make the same turn and only hear the clunk on the first turn. I won't hear it again until I turn the opposite direction.

This is absolutely not the subframe mounts. I had the subframe off of the car two months and the mounts are fine. The RTABs are polyurethane and also are not the problem. The subframe bushings, differential bushings, and RTABs have maybe 2,000 miles on them. I replaced them all just last summer.

Thanks for the thoughts!
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Old 07-08-2012, 10:12 PM   #4
fiveightandten
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Originally Posted by DiscoStu View Post
Thanks for the twist-tie idea. I may actually give that a try. I'm having a hard time telling if there is lateral movement by just looking for markings near the mounts.

This is a single clunk when I change direction. It'll clunk once during the turn and won't happen again until I turn the opposite direction. The 'reset' is when I turn the opposite direction. I can make a turn, straighten out the car, then make the same turn and only hear the clunk on the first turn. I won't hear it again until I turn the opposite direction.

This is absolutely not the subframe mounts. I had the subframe off of the car two months and the mounts are fine. The RTABs are polyurethane and also are not the problem. The subframe bushings, differential bushings, and RTABs have maybe 2,000 miles on them. I replaced them all just last summer.

Thanks for the thoughts!
Gotcha. That definitely sounds like it's suspension or structurally related. Just to be clear about the RTAB suggestion I was making, i'm referring to the RTAB carrier, not the bushing itself. We see failure in the welds that hold the carrier in on E36's pretty often. It's not inconcievable that an E46 could fail there. What you're describing is exactly what happens.

This is me prying on the carrier on my friend's E36 M3:


That car was making a loud pop when changing direction, mostly at low speeds.
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Old 07-08-2012, 10:30 PM   #5
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Good video. Like I said the subframe was out recently, and thus the RTAB carriers were out. There was no rust, nor did any of the mounts seem loose. I'll definitely give them a look though.
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Old 07-08-2012, 10:34 PM   #6
fiveightandten
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Good video. Like I said the subframe was out recently, and thus the RTAB carriers were out. There was no rust, nor did any of the mounts seem loose. I'll definitely give them a look though.
Yeah, have a look at the pockets for sure. You never know if they got overtorqued while the car was being aligned, or the stiffer RTAB's pushed a weld over the edge of failure.

I didn't see you mention RSM's. Are the towers and mounts ok? And you've gone through and double checked all the fasteners in the rear end to make sure nothing worked itself loose a bit?

Disco Stu...doesn't...advertise.
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Old 07-08-2012, 10:39 PM   #7
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I had the shocks out over the weekend. The RSMs are fair I'd say. The rear shocks are absolutely worn (H&R sport cupkit). I'm just trying to get through this year on them before going to something new next year. I only use the car for autocross and track days.
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