"thumping" noise in rear suspension under acceleration
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Joined: Aug 2013
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From: Anchorage
05 CL65
"thumping" noise in rear suspension under acceleration
Just thought I'd ask if anyone has had the same issue I'm having and what they found as the problem.
My car has been making this intermittent and inconsistent banging noise under acceleration since I got it, but I have yet to find the cause. Sounds like a right rear shock bushing. It is much worse if accelerating quickly and even more so if the road is not smooth. It makes a similar noise occasionally over harsh abrupt bumps when not accelerating, again like a bad shock bushing would sound. It definitely comes from the right rear suspension area. At first I thought it was just and extremely loud and harsh traction control as it always made the noise when the right rear would spin and TC would kick in. Also, after installing the Quaife LSD it seemed to happen a lot less. However, it still does it.
I have looked over all the suspension links and nothing is loose or appears damaged. With the car jacked up and rear tires hanging there is no up and down play in the rear suspension like I had in the front strut top bushings which I already fixed. My next step in trying to analyze the problem is to put the car on a ramp style lift and lock up the front wheels with my line lock and watch the suspension while someone in the car does some throttle blips to see if anything moves abnormally,
but that is not something I'm looking forward to trying.
Anyway, if you've had similar issues let me know what you found.
My car has been making this intermittent and inconsistent banging noise under acceleration since I got it, but I have yet to find the cause. Sounds like a right rear shock bushing. It is much worse if accelerating quickly and even more so if the road is not smooth. It makes a similar noise occasionally over harsh abrupt bumps when not accelerating, again like a bad shock bushing would sound. It definitely comes from the right rear suspension area. At first I thought it was just and extremely loud and harsh traction control as it always made the noise when the right rear would spin and TC would kick in. Also, after installing the Quaife LSD it seemed to happen a lot less. However, it still does it.
I have looked over all the suspension links and nothing is loose or appears damaged. With the car jacked up and rear tires hanging there is no up and down play in the rear suspension like I had in the front strut top bushings which I already fixed. My next step in trying to analyze the problem is to put the car on a ramp style lift and lock up the front wheels with my line lock and watch the suspension while someone in the car does some throttle blips to see if anything moves abnormally,
but that is not something I'm looking forward to trying. Anyway, if you've had similar issues let me know what you found.
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CL65
I haven't experienced this but I thought I'd ask a few questions. Does it do it in dyno mode or with traction control shut off? Does the car jerk or express movement when in the driveline or suspension when it happens? Is the exhaust hung and secure? Do you tires show any rub marks? is it at slow speeds, possible wheel hop? did you notice it at the track with drag radials?
Thread Starter
MBWorld Fanatic!
Joined: Aug 2013
Posts: 1,077
Likes: 80
From: Anchorage
05 CL65
Answers in italic.
I haven't experienced this but I thought I'd ask a few questions. Does it do it in dyno mode or with traction control shut off?
Yes
Does the car jerk or express movement when in the driveline or suspension when it happens?
No
Is the exhaust hung and secure?
Yes, that was actually the first thing I checked. I was hoping that was the cause since it would have been the easiest fix.
Do you tires show any rub marks?
Nope, plenty of clearance to move up to 295's from my 275's when they wear out. I jacked up the car by the differential and ran it in gear, then shut it off & set it down. The ABC system removes all the pressure from the rear struts when you do that so when you set the car down and the rear suspension fully collapses. It's a great way to evaluate tire clearance.
is it at slow speeds, possible wheel hop? did you notice it at the track with drag radials?
Yes, worse at slower speeds, but I can get it to do it at about 1/3 throttle sometimes when there is definitely no wheelspin and definitely no a bouncing feel like wheehop at all. As for the track, I think it was happening there last year, but to be honest it is harder to tell when lined up with open header race cars and wearing a helmet.
Yes
Does the car jerk or express movement when in the driveline or suspension when it happens?
No
Is the exhaust hung and secure?
Yes, that was actually the first thing I checked. I was hoping that was the cause since it would have been the easiest fix.
Do you tires show any rub marks?
Nope, plenty of clearance to move up to 295's from my 275's when they wear out. I jacked up the car by the differential and ran it in gear, then shut it off & set it down. The ABC system removes all the pressure from the rear struts when you do that so when you set the car down and the rear suspension fully collapses. It's a great way to evaluate tire clearance.
is it at slow speeds, possible wheel hop? did you notice it at the track with drag radials?
Yes, worse at slower speeds, but I can get it to do it at about 1/3 throttle sometimes when there is definitely no wheelspin and definitely no a bouncing feel like wheehop at all. As for the track, I think it was happening there last year, but to be honest it is harder to tell when lined up with open header race cars and wearing a helmet.
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From: Southern California, USA
2003 CL55 AMG
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From: Phoenix
222 S-65
Same issue in my 211 E-55 and 221 S-65.
The 211 car was it tearing the fasteners out of the car that the rear subframe bolts to. Got to cut holes in the car and make up 1/8” thick shims same shape as inside the opening. Weld a nut to the top of it and weld shim into the car. Bolt it together again.
The 221 car developed slop in the subframe bushing. Fixed that with the 222 car.
The 211 car was it tearing the fasteners out of the car that the rear subframe bolts to. Got to cut holes in the car and make up 1/8” thick shims same shape as inside the opening. Weld a nut to the top of it and weld shim into the car. Bolt it together again.
The 221 car developed slop in the subframe bushing. Fixed that with the 222 car.
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