Ok, so I searched for days on here and haven't found any concrete answers for the noise I'm hearing in my car.


It's a 2007 SS/SC with a mu3/LSD 120k on it, had 105k when purchased in 2-15. all stock as far as I'm aware. I rescued this car from a Ford dealer so not much history on it, but appears not to be modified.


Here's what it is doing.
It's making a rotating rubbing sound on deceleration/coasting in all gears.
When I put it in neutral and coast or push clutch pedal in the noise almost goes away, but it's still there but is barely noticeable, but still there.
When car is on lift and I rotate either wheel by hand the opposite wheel turns in the same direction.
It didn't do this till 2 weeks ago.


Here's what it's not doing.
Does NOT make the noise under acceleration or while rolling and lightly touching the gas to remove drivetrain lash.
No hard shifting, no grinding between shifts, no vibrations or clunking.
Turning from side to side while rolling doesn't change the sound.
While car is on lift turning the wheels manually there are no rough, rubbing, dragging noises.
No excessive play on axle shafts when I push/pull up and down on them.


I know there's been many post on these transmissions and noises, but I haven't found a definitive explanation to the cause, no smoking gun so to speak. Can someone tell me for sure with this information what exactly the culprit is or at least with a 95% certainty what is causing this noise.
Thanks for taking time to read this and any help

 

If both front wheels are suddenly rotating the same direction on a lift then that pretty much tells you there's some serious transaxle issues going on.


Sounds like something wrong with your carrier perhaps? But then again I'd think it would be virtually silent until you turn.

I will have a complete F35 for parts soon if you need anything.

 

Thanks firehawk for your reply, I'm from old school and thought that a way to check LSD is if you rotate the left wheel in a forward direction then the right should rotate in the same direction. At least that's how my older vecicles and 02 z06 work, I thought this would act the same, and looked at this G85 as the diff was functioning correctly.


And I'm not sure that it just started all of a sudden, it was just something I checked while looking for something a mis with this thing. I never had a fwd issue before so not completely sure how these are supposed to function, or how the power gets applied through one of these.


So, are you saying that when both wheels are suspended in the air and you rotate one side the other side should "not" rotate.


thanks

 

The other should rotate the opposite direction if the car is up in the air and the trans is in gear preventing the carrier from rotating.

Quaife is not a clutch type or friction type LSD.

Limited slip differential (LSD) - Quaife


Clutch type LSD *what you're used to*

 

Thanks firehawk, I read the text and watched the video. So in the ss diff there are gears that transfer lateral force and the z06 has the clutch packs to do that.


I didn't have the trans in gear, therefore the carrier was just spinning, not reacting like it was powered since I had it in neutral. So I should put it in gear with someone pushing in the clutch and when I turn one of the wheels, they should spin in opposite directions, correct? If not then the diff is toast?


Today when I got home, in my driveway I got tires spinning and from the evidence left on the blacktop both tires were spinning. So that would lead me to believe the diff is reacting normal, correct?


I'm never to old to learn.


thanks for the good information firehawk,

 

I'm not sure what your Z06 has but the clutch type is very common for OEM.

You want to put your cobalt in gear to stop the carrier from spinning then spin one of your tires. No matter what OEM differential is in your cobalt they should spin the opposite direction.

The only way to know 100% for sure that you have a quaife is to pull an axle shaft out and look in your carrier. Yes you can look for the G85 RPO code in the trunk *cobalt* or look for the LSD stamp on tag that's on top of the trans but neither is proof that it hasn't been swapped in the past.

There will be no cross pin between where your axles go into the diff.


EDIT: The test in gear for the clutch pack type will also spin the wheels the opposite direction but it will take quite a bit of effort to get them spinning. You have to overcome the friction of the clutches but it's 100% doable by hand. The in neutral, spin the wheels and see if they go the same direction works well for the clutch type diff's. I prefer to put it in gear and spin to see how tight the clutches are though.

 

Ok so getting ready to pull the transmission for what sounds like a bad bearing, and I just removed the intermediate driveshaft going to passenger side and the bearing is rough as heck and making a significant noise when spinning by hand. I know it is dry and worn and will be replaced but do you think this could be where all my noise is coming from. Has anyone else had this bearing go bad and what was symptoms that led you to this bearing

 

i have heard of those bearings failing before. id replace that before you yank the trans out, you have a known bad part there, would suck to pull the trans and rebuild it just to find that the steady bearing was the problem the whole time

 

That's what I was think sharkey, and if I replace bearing and it wasn't the culprit than l'm not out alot of time and work, it won't take as long to get to this point again. And yes this bearing is noticeably rough and noisy so it may just be my problem.

 

And super easy vs splitting the trans.

 

So after thinking about it I decided to remove the transmission after all. Reason is with my luck I would have replaced the intermediate shaft bearing and that probably wouldn't have fixed my issue, and even if it did fix noise with 120k on car would probably have to pull to replace clutch some time in near future.
My question here today is, I have a GM service manual for this car and it says not to resurface this flywheel, I already ordered new GM friction disc, pressure plate and release actuator. I know I've read a lot on this forum where flywheel replacement is pretty common, but is it necessary, car is all stock, or are these flywheels serviceable but GM just wants to sell new parts?


thanks larry

 

Buy a new oem flywheel.

 

What's involved with replacing the bearing? My transmission has been making noises for over year now, suspected intermediate shaft bearing failure.

 

Now that I think about it my transmission is also kinda getting louder

 

The intermediate driveshaft bearing is pretty easy to replace, after the passenger side driveshaft is removed there is 3 bolts that hold the bearing housing to engine block. Remove them and the shaft assembly can be removed from the car. Then remove bearing and shaft from the housing, remove one snap ring and remove bearing from the shaft. Install new bearing onto shaft and shaft/bearing assembly into bearing housing then reinstall into differential and secure with 3 bolts onto engine block.

 

So I took my transmission to a local transmission shop with a very good rep, and highly recommended by a friend that I respect his advice on car stuff.


I asked him to call me when they get it apart, so today they called and I stopped by. Every bearing in the transmission has significant wear, flaking on most of the rollers. Only hard parts that have wear is the 5th gear engaging ring, instead of cogs having sharp ramps they were all rounded off. He couldn't believe there was no problem shifting into 5th gear.




Now with 120k on transmission I still think the bearing wear is excessive, unless the wear on the 5th gear engaging ring wear contributed to the bearing wear. Not knowing the service history of this car, I'm not sure the trans oil has ever been changed before I changed it three weeks ago. I didn't change it when we bought it in march 2015 because the dealer we bought it from said they did a full service on the car. Anyway it will be getting all new bearings inside and a new 5th gear engaging ring. Even the differential bearing rollers were flaking/pitting.


Just has the look of fine metal being ran through it, but really all it would take is for one bearing to fail and if driven long enough it would lead to the metal getting into and damaging all the rest.


And come to think of it, the noise started around the middle of October, so my daughter said, when I drove her car back in early November. I asked how long has this car been making this noise, she replied "a couple weeks now, but it doesn't seem to be getting worse so I didn't think it was a big deal". I think we found a big deal now!!

 

Well I just want to update all on my transmission noise issue. I received my transmission back from the trans shop this past Monday, and got it on the road Wednesday, and the transmission is working great and the noise is gone, and the car feels and sounds great. I did some other things in the course of this repair that was much needed and some things just because it was a convenient time to do them, to include front wheel bearings, intermediate shaft bearing, front lower control arms, stabilizer bar bushings and new end links, clutch was operating fine but replaced with GM new parts while it was apart, and replaced the charged air coolant circulation pump that wasn't working. The car drives better and handles better with no clunks or noises when going over bumps.


And thanks to all that gave advice on this matter, especially LsCobalt07 who supplied the link for the 5th driven gear that I so desperately needed.