RunYun

Just gonna have to keep trying to figure it out. It is worse in the am so the Proxes could be flat spotting. At times it drive smooth as silk and others not so much. Maybe I just feel more of the road than the G35. Still fun stomping the gas and jumping to 90 like it's nothing. :-)

Stone17

iTrader: (3)

What part of Houston do you live at?

RunYun

Cypress area.

Darkman

iTrader: (2)

Most highway speed vibration issues turn out to tire/wheel related and that be the case here.

Another possibility, that is not uncommon, is a transmission issue descibed in the TSB referred to already. Specifically, the Tremec has a known issue with 6th gear. If this is the problem, it is easy to verfiy because you can always stop the vibration by simply shifting into another gear such as 5th or 4th and maintaining the same speed.

RunYun

Very unsure at this point. Car sat in garage for three days while I was on a business trip. Drove it today and smooth as a babies ***. Only thing done over the weekend since I last drove it is I washed it. WTF? I pushed it to 95 on way home and some minor vibes, but not like before. Almost got balanced last weekend, but didn't.

RunYun

Drivers side motor mount changed under warranty and car is tight and right. Gear changes are smoother very light vibration at high speed, but much much better.

Closer_2001

iTrader: (6)

Ding Ding Ding winner...!!

I am bound not to discuss this based on a GM Repurchase.

Closer_2001

iTrader: (6)

If you shift to 5th and it goes away, you have one of the bad Tremecs.

RunYun

I will try the 5th gear thing again, but I don't remember it making a difference. Still very minor vibration at hwy speeds, but much better since motor mount was replaced.

Brian68

I am sure to be corrected if I am wrong, but I think the only model years affected by the sixth gear vibration is 04 and 05. One of the first things I look at is the drive shaft. If the bolts are all tight, the center bearing is not shot, and the front joint is not ripped, put the car on a lift and idle it in 4th or 5th gear, watching to see if the shaft is bent. You can also change the phasing of the shaft to the yokes (front, back, or both) to find a better balance point. Did they check to see if both engine mounts were broken? That happens a lot.

Closer_2001

iTrader: (6)

You are correct - but I wouldn't bet on the same issue not being possible in other years.

RunYun

I will take a look at the drive shaft too. It's just odd today on the way home vibration. Not as bad as before the motor mount, but worse than it has been recently. Just does not make sense why it would come or go. If it was a bent shaft, out of balance shaft, bad gear etc it would be constant. The other mount looked and felt fine, but I guess you never know. Maybe something in the drive is bad and mount are just masking it. If mount fail again shortly it will surely mean something back there is going on.

Rakenjevnk

I am chasing a vibe as well, when I switched from my winter to my summer tires it got allot better but it's still there. When it happens I can see my shifter vibing, it happens in 5th & 6th so I don't think it's tranny. I have new CS motor and tranny mounts so the drivetrain should be solid. I am guessing it's a combination of slightly bent wheel and driveshaft out of phase because it comes and it goes (probably because the harmonic won't resonate when the wheel changes phase-relation with driveshaft due to turning?) and changes slightly when I rotate my wheels.

I also have a loud hum @ 110 mph+ and I have never changed any suspension bushings so it could be allot of small things adding up... When i jack up the car and shake the **** out of all the wheels they all seem rock solid though. I guess my arms can't simulate going 110

speedbikelvr

iTrader: (7)

Dont know if this will help anyone but I was dealing with a vibration for awhile with my car also, tried looking at everything and couldnt figure it out until my harmonic balancer came apart and went into my fans. put a new one on and the vibration was gone.....

Rakenjevnk

I was just looking for a sale on the ATI balancer and then I want to put it on but it is hard to find one for a deal. $450 is a good chunk of change for a pulley with rubber in it

vetteboy99

Take it to the dealership brother. It's under warranty

RunYun

Had it in to my local shop for an oil change and asked them to look at it. They are very aware of the issues with the CTS V's and quickly found 1" of play in the carrier bearing. They called the extended warranty people "Easy Care" and they made them pull the drive shaft after getting my permission to confirm. This was a waste of time since it was obvious. Then they told them to only change the bearing. I thought the whole drive shaft had to be changed. They apparently have the same view on this and told them they would not do a half *** job. So they recommended I take it back to the dealership since they may have more pull. Can only the bearing be changed out? Is that ok given it has been flopping around for some time in that bad bearing? I hope this is the issue, but my shop said they still needed to check the CV joints to make sure they were ok too. Anyone else have experience with this Easy Care? I bought the warranty through the dealership I purchased the car at. bTW I don't normally buy these, but my buddy got it for a very low price.

Rakenjevnk

I am sure that the stock drive shaft and carrier bearings are sold as one piece and that the carrier bearing is somehow bonded or you cannot split the fore/aft portions of the shaft to do a replacement.

D Block

iTrader: (1)

glad u found it man. i just had my driveshaft replaced also about a month ago. Mine was a lot more obvious though, and vibrated very badly in all gears and all speeds.
GM considers the carrier bearing a non-replaceable part, so you must replace the entire shaft..... Or so i was told. lol

BudRacing

iTrader: (3)

^^I might be in the same boat soon enough. For now I'm hoping a tire balance will help. I'm at 105k and I know my carrier bearing sags a little, but it's not torn or making noise.