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Discussion Starter #1
This is my first post to the forum but my wife and I have owned a Cadillac for a few years now. It's her daily driver. 2011 Cadillac CTS 3.6 2 door. So far we've only had an issue with the front left hub and that was replaced under warranty free of charge which might I say our local dealership seemed on point. The bumper to bumper warranty just ran out this month and wouldn't you know it another problem comes up. There is a rattling sound coming from what sounds like the rear end at 40 to 50 mph. It doesn't get worse with acceleration and it stays about constant whether off the gas or cruising between 40-50.

I got under the car to see if it was a heat shield or something else rattling. I couldn't find anything loose. I pulled the rear seat out and had her drive it while I stayed in the back with my ear to the floor. It's definitely coming from the rear end area. I can't see CV axles making that noise, nor the flange where the driveshaft bolts to the rear gear box. The only thing I can see that would make that noise would be the gear box.

So she takes it to the dealer who once was very helpful assuming that the rear gearbox would surely be under the powertrain warranty which is still in effect. They tell her that a noise diagnosing fee could be 2-3 times more than the normal diagnostic fee of $135 and that we have to pay for this fee even if it's under warranty.

Does this make sense or is this dealer not doing things right? I 'm thinking a warranty is a warranty and sure I can see paying the fee if it comes back and it's something not covered under powertrain being the problem but for it to be the rear end I wouldn't think we would have to pay anything.

Anyone have any ideas what it could be or any known issues out there with the rear ends? I've searched with not much luck.
 

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2008 CTS
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When speaking to the dealer you should just say that you hear a noise in the back end. If they diagnose it and the problem is under warranty then everything is free. If not under warranty, the diagnosis and the repair is on you.

In my opinion most dealership staff belong in cell.

I wouldn't be surprised if the noise is a bad wheel bearing. With the car on a hoist and running in drive [be very careful], the noise may be pin pointed using a stethoscope.
 

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Discussion Starter #3
Im gonna give it a shot and see if I can pinpoint it. Just scary being under there while the speedo is on 50 mph. I would think a wheel bearing would make a constant sound this sound is just at 40-50 mph.
 

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2011 CTS-4, Sedan,Tuscan Bronze
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Check your rear sway bar links and see if they have any play in them. They should be tight.
You are correct that a bearing will make a constant noise. It is more of a humming sound than a rattle.
 

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Discussion Starter #6
I put the car on jackstands and got under it with a stethoscope while she was inside feathering the gas producing the noise. It took a while but I finally figured out what it was.
One of the bolts on the front of the driveshaft where it goes in the transmission was loose. There is a rubber flange and bolts through it.
One of the bolts had worked loose. Tightened it and no more noise. It's kind of disturbing though why that would work loose as it's definitely not a maintenance item.
Has anyone else had this problem before?
 
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