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Discussion Starter #1 (Edited)
Finally got the UUC bushing installed by the dealership. Lucky me I was able to convince them to install it under warranty as this would be the 5th differential on my 04 V. Got a call from the service advisor suggesting I replace the diff fluid with the GM fluid and additive as they noted the diff whining. I denied the service as I just replaced the fluid with Royal Purple about 500 miles ago. On the drive home I was a bit disappointed that the clunk is still noticeable. Just a slight improvement between shifts. The whining is actually louder than I thought it would be particularly at cruising speed between 60-80mph and acceleration. I guess this would be a good time to try AMSOIL Severe Gear 75-90 and Slip Lock. Hoping it could quiet down the diff a bit. Next plan is to replace the stock motor mounts with the UUC mounts. I'm a little hesitant as my stock mount were just replace about 15,000 miles ago. Hopefully the mounts will further reducing the clunking.
 

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2016 ATS Premium 6-spd MT
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Seems like the reason GM did it the way they did with soft bushing, etc was to reduce whine.

By "fixing" it, we add Specter Werkes bushings, and the whine increases.

Then, we add a KARS III kit, and the whine increases.

Then, we add a UUC diff bushing, and the whine increases further.

Maybe, we should just let the diff develop the whine on its own and save our money on so-called "fixes!" :alchi:
 

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Discussion Starter #3
Guess if I want a whine free car, I should have just stuck with Lexus and Acura. I expected higher standards prior to buying the V. It's disappointing that by trying to fix a problem, there's a compromise somewhere else. This is just one of a few major problems I've already encountered with the V. Thank god for the warranty. I'll just keep her until the warranty expires. Until then, I think straight pipes should be next on my list. The noise would be more exciting.
 

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2018 CT6E, old: 2014 XTS Vsport, 2005 CTS-V, 2004 CTS-V.
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Use heavier weight Royal Purple if your at roads end. 75w130 or whatever is the next step heavier. It will make a noticeable difference for harder any cost.

Norm
 

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Chatter is the problem if the fluid is not right, not whine.
Whine is an indication of a ring and pinion clearance issue and some of it is normal.
They are mechanical gears and they work. You can't expect them not to make any noise, although I'd be the first to confess that the older diffs can have serious issues.

As stated, all the "fixes" for the rear end to solve wheel hop and the loose bushing will add to noise in the cabin by small amounts.

The V is prone to clunk for several issues, not all of them are related to the diff, and not all of them can be eliminated by replacement of factory parts.
 

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'05 CTS-V, '00 SLS, 98 SLS, 89 Eldo, '80 Eldo
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With my car, bad motor mounts added to the clunk. Did the diff bushing, but the clunk came back. Not too bad though. After I did my springs and shocks, it got real bad. I thought I went too far with the mods, cuz on a bumpy road, the V was rattling like an old hoopty. Luckly this was only for a couple days, since I already had an appointment to get me MMs changed. Both of mine were bad. This was back in July, and my V is 95% clunk free. The only clunk I get is when I press the clutch pedan in while in first gear and at meduim RPMs. Very rare though.

Tony
 

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'06 Z06, '05 CTS-V 453rwhp/434rwtq (sold)
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Discussion Starter #11 (Edited)
I really love the car. Fact that this is my first domestic car as well. Compared to my other cars, (yes they're Japanese cars) I'm just not used to the whines and noises the V makes which is considered normal operating conditions according to the dealer. On top of that, I'm just surprised how many major mechanical repairs this V has gone through before it even hit 55,000 miles. Most recent is the replacement of the power steering rack. The entire drive train is practically new since the tranny was installed at 26,000 and the 5th rear diff around that time. Even this morning as I'm shifting through the gears while at park, the noise through the shifter, linkages, and pushing the pedal in transmits a slight clunk throughout the tranny all the way back to the rear diff. And when I shut her down, the shuddering or "dieseling" sound of the engine is just bizarre. Motor mounts were recently replaced as well so they should not be the cause. I have a feeling that no matter what I try to do that these clunks, whines and noises will not go away. I just have to accept that it's simply part of the car's "normal operation." Seriously, if the car did not look as good as it does and did not produce the power it has, it would have been for sale right now. The only thing that I'm looking forward too now is putting a maggie on the V. I'm hoping to stay patient for now.
 

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'05 CTS-V, '00 SLS, 98 SLS, 89 Eldo, '80 Eldo
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Some have more problems than others. I've been lucky so far. But, to a point, you have to keep in mind, this is a hot-rod. Your not gonna get the best of both worlds. The CTS probably doesn't have any of these problems.
That said, I can understand your frustration. Your V seems to a lot more problems than the rest of us.

Tony
 

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LS engines in these have a pretty awful spin down time, if the mounts are bad it will shake the whole car.
We do see lots of mounts.
What I refer to as the '08 style diff is pretty reliable, anything before that seemed to have issues. The older they were the worse they were.

Some of that clunk is from the dual mass flywheel and some is just from the geartrain.

"Normal" is a matter of opinion and perception. What might be normal to your dealer might not be to me.
 

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2018 CT6E, old: 2014 XTS Vsport, 2005 CTS-V, 2004 CTS-V.
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Must be a "chrisism" thing!

Show me a jap sedan that is warranteed with this much torque? GTR don't count as the 18,000 mile service costs $2,000(see Edmund's).

Norm
 

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Ewill,

Mine is going to need it's first replacment diff soon due to whine. I have around 28K miles. I will be out of warranty by the next time I need one.

I knew the 06/07 was better but didn't know about the 08. How can I be assured I get this 08 version? Is there a way I can check with a part number to see before the dealer installs?

My dealer isn't at all impressed when I ask questions like this. I know they are thinking hmmm another internet expert.
 

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If they are installing a new unit then you will get the '08 style diff.
All the old parts are removed from GM stock and the only pieces you can get are the latest design part.

There are a couple of threads with photos of the primary difference between the two, you can tell by looking at the pinion housing.
The seal and yoke are different as is the housing itself. This new design seems to hold up better, I think it is structurally stronger but don't quote me on that.
Just make sure they put in the friction modifier first, then fill the fluid.
 

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'05 LS6 V Stealth Grey; '14 Z71 SLT Sierra 1500 Stealth Grey
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I had my bushing installed today. He also drilled and replaced my broken exhaust bolt. He told me the bushing being replaced was not good but not destroyed. The guy also said my Kars III bolts attatching to the outside subframe/welded plate had come loose. Upon driving home and taing a cruise earlier I notice the car hooking much better. don't know if that's the bushing or the bolts. If it's the bolts, that's scary how different it is/was. With that, does just the diff bushing create that much of a difference?
 

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2016 ATS Premium 6-spd MT
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Got mine done yesterday. The biggest thing I noticed was an increase in apparent driveline "lash" for want of a better term. Could be that the softer OEM bushing deguised or masked that before or maybe I just wasn't tuned into it before.

(Dang! Hope they get this MM issue resolved now. :rant2: A company can do 1,000 great things, but it takes just one FU to F things up.)
 

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'05 LS6 V Stealth Grey; '14 Z71 SLT Sierra 1500 Stealth Grey
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What do you mean by "lash?"
 
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