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2005 STS V6-1SC
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Discussion Starter #1
Hello! I just joined this is my first cadillac 2005 STS It had 18798 miles verified through 2 different reporting agencies(carfax & autocheck) The car was pre-owned certified by the dealer and is in great shape, fully loaded. The only problem is that there is a low-speed rumbling from the rear suspension over rough roads or bumps. At high speeds 70mph+ the car is fine. Is this rumbling and occasional thump normal or is there a fix? I would like to get some owner input before I start going to the dealer or independent shop.
 

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Cadillac Owners Troll
2019 CT6 Sport 3.0TT,2015 Luxury ATS , 2016 ELR, and Volt
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2,398 Posts
From my experience that is the way they are. It's out of character for a car like that. I remember the first time i drove one when they were still in prototype stage and was very vocal about it.
 

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2005 STS V6-1SC
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411 Posts
Discussion Starter #3
That's what I was afraid would be the case. Still I am interested in knowing if there is a fix for it including suspension mods or aftermarket upgrades. Thanks for the reply.
 

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STS
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320 Posts
I would be heading for the dealer as soon as possible to resolve situation. You shouldn't have any noise or rattle from the STS rear.
 

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Cadillac Owners Troll
2019 CT6 Sport 3.0TT,2015 Luxury ATS , 2016 ELR, and Volt
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2,398 Posts
That's what I was afraid would be the case. Still I am interested in knowing if there is a fix for it including suspension mods or aftermarket upgrades. Thanks for the reply.
These kind of things are always difficult to assess over the internet, so it may be worth it to get the car up on a hoist and have a good look at it. Strut mounts, spring isolators,cradle mounts are always suspect, but they haven't been a problem on these cars. There is a mass damping material that can be applied to the rear under-body area underneath the carpeting, but that's a lot of work and probably won't make a major improvement. Make sure your tire pressures are at the recommended pressure based on the door sticker. I know mine has quite a lot of road noise from the rear and everything is fine.Tires can be one of the greatest contributors so that may be an area to look at. Many are rated for noise on various websites such as tirerack.com. Also worn tires can be a major contributor as well. Other than that, I'm not aware of any fix. Shock absorbers/struts can affect the noise as well, but that can turn into an expensive experiment.
 

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Cadillac CT6 (2019)
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2,313 Posts
As was said, tough to diagnose over the Internet. My '06 had an increasing rh, rh, rh noise (that increased with speed) till about 50mph where the whine kind of dissipated. Ended up being the rear end (which was replaced under 'Certified' warranty). If your car is certified, bring that puppy in.
 

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2006 STS 1SG & 2007 STS 1SE
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13 Posts
Make sure there's no way it could be exhaust resonance. There are a number of owners that went to a lot of trouble when exhaust counterweights fixed/dramatically improved similar issues.
 

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2005 STS, 2008 Escalade EXT
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113 Posts
There is a service bulletin for a software update where the rear suspension is over compensating for bumps at slow speeds. Its described as a groaning sound. You may also need a clutch pack or a fluid flush in the rear diff. All of this has been done to my 05 under warranty and problem solved. If someone has access to AllData they could post that bulletin.
 
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