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Discussion Starter · #1 ·
I have an '06 that I bought in 2009, and have put about 50k miles on it. As part of a bunch of other work I've been doing recently, I've replaced the stock clutch with a Spec Stage 2+ with aluminum flywheel, along with the master and slave cylinders, pilot bearing, and clutch line. (That clutch is pretty grabby and engages quick, even with the shim installed, but I'm getting used to it.) I also replaced the engine mounts and transmission mount while I had it apart. The transmission and rear end fluids have both been recently changed as well. Part of that work involved removing the rear axle and driveshaft to get the transmission out.

With everything back together, I noticed it has a whine/moan on decel when driving at speed. So, about 30-40 MPH, let off the throttle, and it will make a moaning sound. It doesn't do it sitting still revving it in the driveway, and doesn't seem to do it when under power.

My first thought was that it was the exhaust hitting the body, but I couldn't find evidence of that. I won a Solo cat-back exhaust at NASSAM this year, and I've since installed it. The exhaust sounds great, but the moan is still there, so I think I can rule that out.

My car does not have the torque arm since it's an '06.

My car is a 2.4, so it did not have a dual-mass flywheel like the GXP cars.

There are no clunks, grinding, shudders, or vibration. Other than the sound, it's fine.

It's possible that it's the driveshaft, but the driveshaft looked good when it was removed, we took care not to damage it, and followed the Helm manual's instructions for installation and bolt torque sequence. I suppose it could be a bad transmission mount but the new GM mount looked good when I installed it. (The old trans mount looked okay too. Those original engine mounts however were way past their useful life.)

I'm wondering if I've either done something wrong when reinstalling the rear, or perhaps the rear end bushings are worn? I don't remember a specific procedure in the Helm manual about bolting the rear back in beyond bolt torque specs. (we didn't remove it from the car, just unbolted it, leaving the axles, etc. in place).

Could one or both of the axle shafts / CV joints have been damaged while I had the car apart and cause this?

I did a quick online check and none of the GM sites I checked show a part number for the bushings, just the crossmember, which is no longer available.

Thoughts on next steps or diagnostic ideas?
 

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2008 Pontiac Solstice GXP - Mysterious (with unkown origin blue sparkle in rear bumper cover paint)
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Just did an aftermaket clutch on my GXP and it “buzzes” on decel. Not sure what a moan sound would sound like from a car.
Is it a single pitch or does the pitch change with either RPM or speed?
Anyway you can post a link to a video with sound?
 

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Discussion Starter · #3 ·
I'm not near my car at the moment, but I'll try to get a video of it. It seems to be a noticeable drone or lower-pitched whine that shows up when you let off the throttle, falling pitch as speed drops, and lasts a couple of seconds. My assumption (!) is that something is rubbing or touching when the driveline moves from decel, but I haven't proved that. It doesn't seem RPM related but I'll try a few more tests. I notice it most in 3rd, 4th, and 5th.
 

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2008 Pontiac Solstice GXP - Mysterious (with unkown origin blue sparkle in rear bumper cover paint)
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Man i swear someone posted a video last year on the forum but i cant find the thread.
I am also not sure that tje resolution was posted.
My (not so great) memory is telling me it turned out to be a heat shield either on the cat or exhaust manifold?
 

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My 2006 manual does the same thing. If I let off the gas around 60km/h (40 mph), I hear this grunt/growl from the rear end. I have found that this occurs more often when the car is 'cold' versus after a highway drive or once it is warmed up.
I have had a couple of shops look at it over the years and they don't see anything wrong. I suspect it may be related to the rear diff with the LSD.

I have put 40k miles on this car in the last 7 years and it still does it. I have just learned to live with it.
 

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My 2006 manual does the same thing. If I let off the gas around 60km/h (40 mph), I hear this grunt/growl from the rear end. I have found that this occurs more often when the car is 'cold' versus after a highway drive or once it is warmed up.
I have had a couple of shops look at it over the years and they don't see anything wrong. I suspect it may be related to the rear diff with the LSD.

I have put 40k miles on this car in the last 7 years and it still does it. I have just learned to live with it.
It is unlikely to have anything to do with the LSD, since that only comes into play when the rear wheels are turning at different speeds. It is more likely due to the finish on the surfaces of the gear teeth, since overrun loads them on the reverse faces.
 

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I'm not near my car at the moment, but I'll try to get a video of it. It seems to be a noticeable drone or lower-pitched whine that shows up when you let off the throttle, falling pitch as speed drops, and lasts a couple of seconds. My assumption (!) is that something is rubbing or touching when the driveline moves from decel, but I haven't proved that. It doesn't seem RPM related but I'll try a few more tests. I notice it most in 3rd, 4th, and 5th.
Does you 06 have the LSD option (G80)? LSD equipped cars require that friction modifier be either in the new differential fluid, or has to be added separately if it does not.
 

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Does you 06 have the LSD option (G80)? LSD equipped cars require that friction modifier be either in the new differential fluid, or has to be added separately if it does not.
The LSD friction modifier prevents clutch pack chatter during turns when the two rear wheels are rotating at different speeds and the clutch has to slip. It will not have any effect in straight line deceleration.
 

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Discussion Starter · #10 ·
My car does have an LSD, with the proper fluid and additive.

Dad and I looked at the car again. I put the car on my QuickJack 5000 (highly recommended, we did the clutch and exhaust installation with it on the QJ at the high position, without any problems. I wasn't sure if it would be worth it when I bought it, but it's been a solid addition to my shop. It was very useful doing the LS swap on my S10 as well as all of the work on the Solstice).

A visual inspection doesn't show anything bent, loose, or rubbing/touching. It made this noise with the factory exhaust. I've since installed a new Solo cat-back exhaust, and that didn't affect the problem (but it does look and sound better than stock. Solo makes a good product).

On the QJ, we ran the car, revving it in neutral both with the clutch in and out, and ran it through first and second gear. We're now convinced it's not in the rear axle. We think the noise is from clutch and/or the transmission.

On the road, it won't always make the noise on decel, but it does sometimes. It also has a vibration between 2500-3500 RPM, most noticeable in 3rd and 4th, probably due to relative engine load.

The clutch feels good -- no chatter, etc. It grabs pretty close to the floor taking off, but it's also a new clutch and a puck clutch, so it's not going to be the same as stock. Between gears feels fine.

The clutch is a Spec Stage2+, balanced with the matching aluminum flywheel, from Dave at PWerks, as part of (and in addition to) his turbo kit. The clutch went in before anything else and it has made the noise since the clutch was installed, without the turbo kit installed.

Spec says the clutch break-in is 500 miles, and I've got a bit more than 200 on it right now, so maybe it's a break-in issue?

@HHGadget I think on your thread there was talk about the clutch and aluminum flywheel making noise (I'll re-read those threads)? As far as I know the 2.4 in my '06 doesn't have a dual-mass flywheel (it definitely does not look like the 2.0 flywheel).

The audio file is not great, but it's the car accelerating and decelerating in 3rd through 2500-3500ish RPM. You can hear two rattles (one is my JPM shifter, I need to fix that...) and the other is a harmonic vibration you can hear/feel. You can also hear the rattle/sound on decel. It does not always make that sound on decel but it is more prevalent on decel in 3rd and 4th, and more common in lower RPM. I don't hear anything at higher RPM -- either it smooths out or the frequency is high enough that it's not noticeable.

MP3 of the driveline sound

Sound really travels through the car, and you're nearly sitting on the rear end, which is what made me think rear axle at first. Now I'm thinking it's transmission and/or clutch noise.

Thoughts?

Thanks,
 

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2008 Pontiac Solstice GXP - Mysterious (with unkown origin blue sparkle in rear bumper cover paint)
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The sound on decel sounds like the puck clutch to me. A little hard to tell and it sounds like it is jumping on decel, not a consistent sound.

on accel i hear a hollow ish metallic sound.

Was that recording up on the quickjack or driving on pavement?
 

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Discussion Starter · #13 ·
The sound on decel sounds like the puck clutch to me. A little hard to tell and it sounds like it is jumping on decel, not a consistent sound.

on accel i hear a hollow ish metallic sound.

Was that recording up on the quickjack or driving on pavement?
That was recorded while driving. We tried it on the QuckJack, then took it for a longer drive.

The clutch is Spec Stage2+ with their aluminum flywheel. It's not a typical 6-puck clutch where there are just 6 pucks, but it's definitely not the same as the stock full-face clutch. Here's a couple of photos of the disc. On the stock disc, the disc hub sits in a recess in the flywheel (as does the Spec Stage2+ clutch designed for the stock flywheel). With the matching aluminum flywheel, they claim a redesigned clutch system that has better drivability. The clutch disc on that setup (which is what I have), the clutch hub faces the pressure plate instead. It looks backwards compared to a stock clutch disc, but it really won't fit properly the other way.

Bicycle part Rim Automotive tire Automotive wheel system Circle
Font Gas Circle Rim Auto part


I just finished putting the turbo kit on it, and the tune's not perfect yet, which explains the jumping. It was a bit smoother, but the same sound, pre-turbo. I've put about 200 miles on it before the turbo kit, and probably 20 since. We're now in the "grab logs, reflash, and repeat" part of the tuning process.
 

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2008 Pontiac Solstice GXP - Mysterious (with unkown origin blue sparkle in rear bumper cover paint)
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@HHGadget did you ever find a harmonic balancer solution?
I found a fluidampr for a cobalt and just broke the budget having a machine shop one off remake the power steering pulley (fluidampr provided the pdf cad of it) i need to drive by one of the local anodizing shops this week and get it hard anodized.. hopefully tomorrow.
 

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Discusion is here:
 

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I found a fluidampr for a cobalt and just broke the budget having a machine shop one off remake the power steering pulley (fluidampr provided the pdf cad of it) i need to drive by one of the local anodizing shops this week and get it hard anodized.. hopefully tomorrow.
Be aware that hard anodizing usually changes the dimensions of the part. When we used to hard anodize aluminum parts we did the final machining after anodizing because the parts would grow.
 

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Be aware that hard anodizing usually changes the dimensions of the part. When we used to hard anodize aluminum parts we did the final machining after anodizing because the parts would grow.
John, I wanted to respond to this as I had previously read that hard anodizing can add to the dimensions and your post was a reminder of that. The place i dropped off this morning said the process should add ~.0001" to the surface (.0002" total but half of that goes into the metal surface, the other half is proud of the original dimensions). In another thread i had mentioned a "perfect fit" but to be more precise, it wasn't an airtight fit so I am thinking i should be okay with the additional .0001" or about a half of a millimeter dimensional increase. I hope....
 
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