Supercharger replacement / Flutter ?

[Admiral Ballsy]

Originally Posted by 2013 ZL1 #7860

You took yours out and compared it to an aftermarket already?

I didn't say (nor would I say) that. Let's leave it here - this last weekend I participated in swapping a coupler on a 2014; it would probably be best for all involved if the actual car remained 'anonymous'. We tried the LPE and a spring coupler generously donated by a forumite. The spring unit was reputed to have been removed at about 300 miles - it looked new, no visible wear at all.

We polished the shaft (hmmmm....) and the bearing surfaces on the spring with microgrit, they were mirror-smooth. We didn't know if that would help with the marbles noise but considered maybe it would reduce the galling, since there's less friction available for the spring to find 'purchase' on the shaft.

The LPE performed identical to the stock. The spring coupler eliminated the noise, but it did have the marbles sound - although not loud, it just sounded like a slightly noisy drive setup. If I hadn't known from videos what the marbles sound was, I'd have put it down to normal engine noise. About 95% inaudible with the engine covers on and the hood down, and totally inaudible from the cabin.

For the purposes of disclosure, we cut some corners since we knew we weren't going to keep the car this way - we didn't seal the snout face, for example, until we were done.

I live ten minutes from RPM transmissions, it's not hard to find helping hands (and LSA owners) in their 'gang'.

Originally Posted by 2013 ZL1 #7860

Maybe an ATI super damper would get ride of some bad harmonics? Just an idea.

I was wondering if anyone made a damped supercharger crank pulley. That's a great idea!

[Admiral Ballsy]

Originally Posted by jayno20

I'd still like to hear this sound. Would you classify it as a "rattle" or more like a "shudder"? I know that sounds weird, but I'm just wondering if what I am hearing is for sure drivetrain noise or if it could be this.

In my experience - it's a rattle. It's not 'felt', at least not significantly.

When I bought the car, last November, the salesman wanted me to test-drive it before we did the paperwork, to make sure it was what I wanted (I had ordered it; I'd driven an A6 CTS-V sedan, but obviously M6 wagons weren't exactly bursting off the lot). It made the noise every time I pulled away from a stop; we both thought "exhaust rattle, no big deal, we'll fix it".

After about a month, and some accumulation of other little issues, I took it back for the fix. They took care of everything except the rattle; I said "you couldn't hear it?"...they said "oh, we can hear it - everybody who drove it did".

One guy thought it was differential, and it does sound like it's coming from the back of the car - when you're in the cabin with the windows up. If you open the driver's door, though, and listen, you can tell it's coming from the engine compartment area.

Anyway, they called GM and were promptly given a TSB that basically says "high performance cars are noisy - it's all normal". I think the TSB was mostly aimed at the fact that T56/TR6060s are just noisy transmissions, but as I said elsewhere I've owned a few and I'm used to that.

So I went to work on it myself. The first thing I found was that the exhaust rattled. I don't know about the ZL1, but the CTS-V has a one-piece system - everything from the front cats back is welded as a single unit. But the angle on the flange on one side was wrong and it rattled in certain conditions. To their credit, the service folks replaced it. And that reduced the rattle - but didn't eliminate it.

Then I found that there was a loose pipe in one of the new mufflers, and I could make it rattle by wiggling the tailpipe. I was *just* able to put a stick down the tailpipe and tack-weld it - but that didn't fix the rattle.

So I went to RPM Transmissions and asked them to tell me what they thought. They were pretty sure it was flywheel noise - these cars have a dual-mass wheel with springs and counterweights, as they put it "there's a lot going on in that bellhousing". And I went to another Cad dealer, a much larger one that sells a lot of V-series. They said basically that they're noisy cars, they'd not noticed my particular complaint but that they had replaced a few noisy flywheels and that your chances of getting one quieter than you started with weren't great.

And that's where I left it until a fellow on LS1tech suggested slipping the blower belt, last month.

I was convinced it was either driveline or exhaust because it sounds EXACTLY like something in the exhaust rattling against the car - metal on metal. It only happens when taking off from a stop, starting when the clutch starts to take up...or when I'm in gear, idling...in a parking lot, say...and I then start to accelerate slowly. It passes through a 'band' of operation where the noise exists, then as the engine leaves that 'band', it vanishes - definitely like a resonance, and it's generally impossible to keep it in that band since the engine has to be loaded. About the only time I can make the noise for more than a split-second is when going up a steep incline - like putting the car on ramps.

[Kevlar382]

Originally Posted by silverds

If not for the 580 HP Supercharged 6.2L V8, why did you choose the ZL1 over an SS or 1LE?

Mag Ride, heavy duty drive train, better looking, was supposed to be limited production, and a few other things

[Kevlar382]

Originally Posted by 2013 ZL1 #7860

Nothing man made is perfect, even when it is new...

Looking for perfection in every single way will only leave you disappointed and lonely.

Good luck with the next purchase...

True, nothing is perfect but the ZL1 has way to many problems.

[chevi286]

Had a 2002 Trans AM Ws6 made the same sound when accelerating in first and only for a second. Sounded like a momentary slight rattle or dieseling in the engine. Contrary to some public perception, it was a great car. Ran very low 13s in the quarter mile stock

[Admiral Ballsy]

Originally Posted by chevi286

Had a 2002 Trans AM Ws6 made the same sound when accelerating in first and only for a second. Sounded like a momentary slight rattle or dieseling in the engine.

That's T56 noise - and IME that is normal. My '99 SS did it, my Corvettes did/do it. I haven't heard it in the CTS, but the SC rattle happens in almost exactly the same circumstances so it's hard to tell.

[chevi286]

If it is then it sounds exactly the same

[jayno20]

Originally Posted by Admiral Ballsy

It only happens when taking off from a stop, starting when the clutch starts to take up...or when I'm in gear, idling...in a parking lot, say...and I then start to accelerate slowly. It passes through a 'band' of operation where the noise exists, then as the engine leaves that 'band', it vanishes - definitely like a resonance, and it's generally impossible to keep it in that band since the engine has to be loaded. About the only time I can make the noise for more than a split-second is when going up a steep incline - like putting the car on ramps.

Are you saying it will make the noise if in gear, while idling, and the clutch is pushed in? Or do you actually have to be starting to move for it to happen?

[Vroom]

My noise depends on the intake air temp, as far as I can tell. when the car is hot, like from idling for a while, then I can hear the noise anywhere below 1000rpm. It sounds like a solid bearing/gear noise.
Its tolerable, and by god I'm stretching that word, at normal temps. (190 ECT, 70-80 IAT). Still hear it, but not as loud.

What I know for sure is I can't sell the car like this. Question is, when do we get the law suit together for the diminished value?

[chevi286]

68,000+ miles on a 2013 will probably be your bigger culprit for diminished value

[Admiral Ballsy]

Originally Posted by jayno20

Are you saying it will make the noise if in gear, while idling, and the clutch is pushed in? Or do you actually have to be starting to move for it to happen?

No, you have to be moving. The engine has to be loaded, but not *too* much.

The best way for me to reproduce it is to drive up an incline, like putting the car up on ramps.

[2013 ZL1 #7860]

Originally Posted by Kevlar382

True, nothing is perfect but the ZL1 has way to many problems.

Funny, my ZL1 has none... Please describe many problems for us???

IMO: making a big deal about a small thing found in almost all Eaton blowers I have ever been around will cause the value to diminish...

[CRTZL1]

Originally Posted by 2013 ZL1 #7860

Funny, my ZL1 has none... Please describe many problems for us???

IMO: making a big deal about a small thing found in almost all Eaton blowers I have ever been around will cause the value to diminish...

+1 ....
I Also have none..
Knock knock on wood....

Sent from my SM-N900V using Tapatalk

[Vroom]

Originally Posted by chevi286

68,000+ miles on a 2013 will probably be your bigger culprit for diminished value

68k miles with no noise I can sell...
68k with the rattle I can't sell and on top of that anybody who's heard it likes to remind me was a piece if crap it and GM are. Diminished value and emotional distress right there