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2004 CTS-V
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Discussion Starter #1
No luck finding this specific problem with a search, hope this isn't reposting.

2004 CTS-V 123k miles. I replaced diff fluid at around 100k due to groaning on turns. That fixed that. I replaced rear wheel bearings within the last 5k. This sounds sort of like mild wheel bearing failure, but idk.

I get a groaning at all speeds and regardless of wheel position. It sounds rotational in that it RRRRrrrrrrRRRRRrrrrrrrRRRRRRrrrr if that makes sense. Anything I can do to troubleshoot before I take it in?
 

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Premium Member
2005 CTS-V
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8,363 Posts
It may be the chatter that the clutch pack makes once the friction modifier in the fluid deterioates. If that is the case the sound should be similar to the one that caused you to change the fluid last time. The best way to hear is to drive slowly in counter clockwise circle with the driver's side window open.
 

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Discussion Starter #3
I'll check when I go to lunch. If that's the case, I'll need to recharge the fluid, I guess? Is that indicative of a larger problem? It hasn't been that long.
 

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2005 CTS-V
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Assuming a fluid change resolves the problem I don't believe it would necessarily indicate a larger problem other than your particular clutch packs "like" a friction coefficient that requires more friction modifier. Since the chatter results from the clutch discs "refusing" to slip (sticton) it would not, for example, suggest failing clutch discs.
 

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Discussion Starter #5
I did the counter clockwise circle test and didn't hear it. It is pretty audible with the windows hp driving though. I'm beginning to think it's tire noise. I have never had such noise from tires, though.
 

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2005 CTS-V
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Going back to your original post and the description of the noise - the "RRRRrrrrrrRRRRRrrrrrrrRRRRRRrrrr" sound signature, coupled with the absence of extra noise in slow speed turns, does seem to point back to a wheel bearing or possibly a constant-velocity joint on the axle.

There are some tires that develop uneven wear patterns and become noisy, and there tires that become noisy simply from age/even wear. What kind of tires? And, are wearing evenly?

One way to check the general condition of the differential is to pull a fluid sample for used oil analysis by someone like Blackstone Labs. I did this with my first differential because some were reporting noisy units that failed and some were reporting noisy units that lasted a long time. (Mine was junk.)
 

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17 xt5 & Blk 05 cts-v
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Change fluid first. Make sure to add the additive. Then let's us know what happens.
 

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2004 CTS-V
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Discussion Starter #8
I'll do the fluid again as I bought too much the first time and had enough for twice. It's the Royal Purple which I had read then doesn't need the additive.

Darkman, the tires are Falken ZIEX ZE612 (cheapos) oem dimensions. I had them rotated last week and they said the passenger rear was wearing a bit faster.

I should have time tomorrow to swap fluid.
 

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2005 CTS-V
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Royal Purple does already contain friction modifier for use in limited-slip applications, but that does not necessarily mean it requires no additive to work in any particular differential. Amsoil Severe Gear, for example, already contains friction modifier and yet many V owners find some more additive is required.

I am not familiar with those tires, but perhaps someone else can chime in about their noise characteristics. If you rotated them however, and the noise did not change it may not be the issue.

http://www.cadillacforums.com/forums/2009-2015-cadillac-cts-v-performance/296953-amsoil-severe-gear-rear-diff-still.html
 

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Discussion Starter #10
I didn't get an opportunity to swap fluid today. Can I just add the amsoil to my current oil, or should I swap it and do it all at once?
 

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I didn't get an opportunity to swap fluid today. Can I just add the amsoil to my current oil, or should I swap it and do it all at once?
If by "amsoil" you mean the additive - yes. If the issue is the friction coefficient of your current fluid then some fresh additive should presumably cure it.
 
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