Hey guys....newbie to a C6 here. I have an '07 LS2 that has a significant vibration from 3300-3700 RPM and then it clears up above 4K. It does it regardless of speed or motion. I can rev in Park and get it or I can punch it and the kick down does it, or straight acceleration. Sounds like what 30 yrs ago would have been a harmonic balancer vibration. Vibrates the exhaust too so it's hard to pin down. Could be in my head, but I think I smell a burnt rubber smell when it does it. Any ideas?

 

Probably the Harmonic balancer, which is typical on these cars. That's easy to check. Just visually inspect it to see if the hub has separated from the outer ring on the balancer. There's a bunch of pictures on these forums showing what that looks like.

 

If not the balancer, consider the drive shaft. Mine had a vibration that turned into a rattle in the same rpm range. Same conditions. On mine the rubber couplers had collapsed. This pulled the front shaft bearing out of the bearing bore/carrier. Under increased rpm the shaft wobbled allowing the rubber couplers to rub the inside of the torque tube. Eventual the rubber wore off allowing the coupler metal to contact the inside of the torque tube. The local dealer thought it was the Flexplate.

 

if the outer ring has separated from the center you would probably not be giving this advice because the outer ring would have gone thru the hood or out of the bottom

 

What are you, dense or something? On every LS balancer that I've seen fail, the outer ring separated from the hub when the elastomer ring failed, and the outer ring walked in against the timing cover, eventually spitting the belts off. I haven't heard of any being thrown through the hood or out the bottom yet, but I would expect that with your prodigious repertoire of mechanical expertise, you've seen all of that before?
Why don't you try giving someone some useful advice for a change, instead of lurking around on these forums, looking for an opportunity to demonstrate your profound uselessness by making inane comments??

 

Got the beastie on a lift today and it is definitely the harmonic balancer. I can see the rubber separating between the inner hub and the outer pulley and some of the rubber is coming out. Well, guess I know what I will be having done next week.

Any suggestions on the best replacement? Brand, underdrive etc?

 

Best bang for the buck would probably be a Powerbond. The best prices I've seen on those was on Colorado Speed's website.
Or you can get a TFS/Summit from Summit Racing for probably even cheaper.
I wouldn't waste the time putting a stock balancer back on it, especially with all the work you have to do to change it.
If you want the best money can buy, then go for an IW or ATI, which would also allow you to have an underdrive now with the ability to change to stock dia. or O/D as well as 8 or 10 rib in the future (if you were to go FI), by changing the outer ring. The ATI you can change yourself but I think you need to send the IW back to them.
I have an IW and it is a superb piece and their customer service is top
notch.
Glad you found the problem.

 

the outer hub of the balancer is trapped behind the steering rack and cant get out but it is able to do a lot of damage if not taken care of.the cheaper Powerbond hb's are too heavy and not machined for the factory DEW washer.if you use one it would be a good idea to pin the crank to prevent it from spinning on the crank snout

 

Well...frustrating day. So, the good news first...one can most definitely replace the harmonic balancer without removing the steering rack. With the correct puller, it can be accomplished in less than 3 hrs. Now the bad news. My issue was NOT a harmonic balancer.

When listening to the issue, the mechanic saw sparks fly out from around the starter. We shut it down and pulled the starter. Sure enough, there was enough play in the bindex it could move into the flywheel causing it to engage the teeth. I went down to the local parts house and bought a new starter. We installed it. Cranked it up and it is STILL doing it. So, now $1000 out the window for parts and labor and I am exactly where I was this morning.

As Southmsfive0 originally suggested, we are thinking the only available option left is the torque tube bushing allowing enough movement for the flywheel to contact the starter teeth and not the other way around...

 

I hope I was wrong. Bell housing back to rear end has to come out. Doable job but it is a JOB especially the first time around.

 

Hey guys, I just finished replacing the torque tube tonight. It took a little over 3 hrs and we did not have to disconnect everything on the rear. I took a few pics, but basically here are the steps we followed:

1. Remove exhaust and tube cover
2. Disconnect the tube to bell housing bolts
3. Remove the driveshaft to transmission bolts through the hole in the rear housing by spinning the driveshaft through the front inspection hole to align each bold with the acces hole
4. Remove the tube to transmission bolts
5. Disconnect the rear shocks and upper control arm bolts
6. Remove cradle bolts and lower transmission and cradle
7. Slide cradle back about 6-8 inches. We did have to disconnect the brake line at the connection block on drivers side, the ground wire, and the transmission electrical connection. We also removed the calipers when we thought we were going to have to drop the whole unit out.
6. By sliding the whole cradle back, we were able to disconnect the tube to transmission housing bolts and lower the tube out.


Once we had the front splined up we bolted the torque tube to the bell housing and tightened the crimp clamp on the spline. Then we moved the rear and slid the cradle forward back into place and bolted the rear to the transmission. Everything else went fairly easily.

You can see in the pics how far down we dropped and also how far back we had to slide the rear cradle to make the swap.

 

Did this fix your vibration issue?

I did pretty much the same thing due to the rear coupler failing. I still have a slight vibration on hard acceleration though. No vibration during normal driving at any RPM. Only during hard acceleration.

 

Was the flex plate damaged?
Fixed now?

 

Yes, it completely fixed my vibration and the flex plate was not damaged. I finally had an opportunity to put some miles on her this evening and at all RPMs and at speeds up into the triple digits there is no vibration or harmonics. :

 

I have read that there is a possibility that the prop nut, in the center of the wole mess, caan come a little loose and cause the rattle. Fix was said to loosen the nut, add lok-tite, retighten to 60lbs. I'm not a mechanic but do understand enough to scare myself. I do take advice well.

 

That is a FACT! My guess is he had a deteriorated coupler and that was contacting the TT under torque load.

 

AL JAZZ - I do heartily thank you for taking the time to post the pics. I will have to take mine to somebody, hopefully my independent guy, What the heck does a new shaft cost (about) and do recommend a used one?

 

I found a low mileage used unit in Michigan which I purchased and installed. I think the best option would be a complete rebuild including yoke couplers, bearings, and seals. If you go that route, I have my original tube I could ship you to have your mechanic rebuild it first so when you pull yours out you have a newly rebuilt unit to install. Just an idea.

 

I live in a small city, Myrtle Beach. Not sure I can find a reliable rebuild machinest. Am good friends with a great salvage yard. I'll talk with them and make up my mind. Thank you much for the advice.

 

Curious about the fact that the HB was pulled without removal of the steering rack, but was it loosen up a bit to be able to move it around for clearance?
TIA