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Hello
2008 base.
I read the superlong post about the guy with the HB issue and GM denying it was covered for months. Crazy story.
Anyway, my new-to-me car has a bit of HB wobble, but what is acceptable?
Q1) Any run-out spec?
The car is cert pre-owned, and it it was going to break, it would be great if it happened in 12 months.
Q2) How is failure actually determined?
(I assume if it comes apart, that is a clear case. But how about belts squealing, etc?)
All good for now. I'm hoping this is a really low-probability-of-failure event, and like most forums, you only hear the bad stuff. But appreciate all of the info.
Pete; If your belts are chirping, that's the first "tell" that you might have a HB issue in your future.
Pretty much.
No spec, but once the elastomeric insert begins to fail you'll get the chirping and worsened wobble, followed by belt damage, followed by eating the outer pulley race. The "good" news is that it takes awhile.
Mine first chirped at under 30K miles and now I'm at 77K miles on the same pulley, so it's taking its time. I think that the colder weather makes it worse. Where I lived for the last 8 years, 5 with the Vette, it was always the same temperature.
GM actually has specs on it. My Camaro SS was making this noise terribly at the end of the summer and I had to replace it.
#PIP4750E: Belt Squeak Noise And/Or Crankshaft Balancer Appears To Wobble - (Feb 10, 2012)
Subject: Belt Squeak Noise and/or Crankshaft Balancer Appears to Wobble
Models: 2010-2012 Chevrolet Camaro SS
2011-2012 Chevrolet Caprice
2009-2012 Chevrolet Corvette
2008-2009 Pontiac G8
with 6.0L 6.2L Engine (RPOs L76 L77 L99, LS3, or LS7)
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some customers may complain of a belt squeak noise and/or a crankshaft balancer appears to be out of balance or wobbling while watching it with the engine running. In most cases, the wobble is an optical illusion because the design of the balancer gives the appearance that it is moving more than it actually is.
Recommendation/Instructions:
If this concern is experienced, follow the steps below:
1. Push the crankshaft all the way to the rear of the engine.
2. Using a magnetic base, attach a dial indicator so the measuring tip is contacting the rear of the drive belt groove.
Notice: An inaccurate reading may be obtained by measuring the face of the balancer instead of the rear of the drive belt groove.
3. Rotate the crankshaft 360 degrees and note the total amount of crankshaft balancer run out.
◦If the balancer run out is 0.40mm (0.0157”) or less, do not replace the balancer because the run out is in specification.
◦If the balancer run out is greater than 0.40mm, replace the crankshaft balancer and perform step 3 again to confirm that the run out of the new balancer is in specification.
4. If the customer has complained of a belt squeak, also replace the drive belt.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION
__________________ Phone: 484-334-8833 Owner of CULTRAG Performance
GM actually has specs on it. My Camaro SS was making this noise terribly at the end of the summer and I had to replace it.
#PIP4750E: Belt Squeak Noise And/Or Crankshaft Balancer Appears To Wobble - (Feb 10, 2012)
Subject: Belt Squeak Noise and/or Crankshaft Balancer Appears to Wobble
Models: 2010-2012 Chevrolet Camaro SS
2011-2012 Chevrolet Caprice
2009-2012 Chevrolet Corvette
2008-2009 Pontiac G8
with 6.0L 6.2L Engine (RPOs L76 L77 L99, LS3, or LS7)
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some customers may complain of a belt squeak noise and/or a crankshaft balancer appears to be out of balance or wobbling while watching it with the engine running. In most cases, the wobble is an optical illusion because the design of the balancer gives the appearance that it is moving more than it actually is.
Recommendation/Instructions:
If this concern is experienced, follow the steps below:
1. Push the crankshaft all the way to the rear of the engine.
2. Using a magnetic base, attach a dial indicator so the measuring tip is contacting the rear of the drive belt groove.
Notice: An inaccurate reading may be obtained by measuring the face of the balancer instead of the rear of the drive belt groove.
3. Rotate the crankshaft 360 degrees and note the total amount of crankshaft balancer run out.
◦If the balancer run out is 0.40mm (0.0157”) or less, do not replace the balancer because the run out is in specification.
◦If the balancer run out is greater than 0.40mm, replace the crankshaft balancer and perform step 3 again to confirm that the run out of the new balancer is in specification.
4. If the customer has complained of a belt squeak, also replace the drive belt.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION
Outstanding information, Gene. I, like others here, have incorrectly assumed that there was no firm hard spec, but there clearly is one.
0.40 mm is actually a pretty fine spec, so mine is clearly out of bounds, and has been for awhile.
While we're on the subject, can you confirm, as has been said on the forums, that GM redesigned the pulley within the last couple of years, and that the new design pulley is intended to improve performance in the area of failure, and the part number.
Mine only started to chirp on a Saturday and on Monday it was at the dealership getting replaced under Certified Warranty. It had a visible wobble, not much but enough. Next time I'm sure I'll be out of warranty so I will go aftermarket.
Gene why do the LS1 and LS2 GTOs have no balancer problems? I have had 3 and know hundreds of GTO owners and never have seen any problems. I search the LS1 GTO forum and can not find an issue. My 2011 C6 35,000 miles looks like it wobbles but no noise or belt damage.
Wow , that is 1/64 " tolerance . I guess if you can see movement , it's out of spec. !
That depends.
What they are saying is that looking at the front or rear face of the balancer is not accurate. You must gauge the runout inside the belt groove, and that's a lot harder to see.
Outstanding information, Gene. I, like others here, have incorrectly assumed that there was no firm hard spec, but there clearly is one.
0.40 mm is actually a pretty fine spec, so mine is clearly out of bounds, and has been for awhile.
While we're on the subject, can you confirm, as has been said on the forums, that GM redesigned the pulley within the last couple of years, and that the new design pulley is intended to improve performance in the area of failure, and the part number.
GM has redesigned the balancer, however, I don't have exact specs.
Gene why do the LS1 and LS2 GTOs have no balancer problems? I have had 3 and know hundreds of GTO owners and never have seen any problems. I search the LS1 GTO forum and can not find an issue. My 2011 C6 35,000 miles looks like it wobbles but no noise or belt damage.
I have no idea. I've done a lot of business with GTO's and have owned one and you're right, I haven't sold many balancers for them.
Thanks to all for the reply and the HB runout spec.
My 2008 is going to the dealer next week under the GM CPO for what I think is a tire sensor. I'll ask them if they can check the HB. From all the GM reluctance to admit to this issue as posted on this site, I'm not holding my breath they will do anything until its shredding belts by the hundreds. But it does wobble. Maybe each dealer is different.
(haven't measured it per the tech note, I don't have a dial indicator and other stuff to really measure it properly)
(The HB is interesting; when I was younger, I always thought it was just another name for crank pully, not realizing that it keeps your crankshaft from breaking due to harmonics caused by each piston push. But I also never heard of one "failing".)
I always think of a harmonic balancer problem as a slow leak on a tire - the longer you leave it the more likely it is going to leave you in a worse predicament.
From the previous HB voting link, it looks like the HB fails at 30%. That really should be an official recall.
Good news for me. I went to the dealer to have my 2008 tire pressure sensor fixed under GMCPO warranty. I asked them to check the HB becuase it did wobble quite a bit to the naked eye, and they agreed it was bad and will replace it. They need to order it and it will be scheduled in a few weeks. I hope this will last many years and am very happy with this dealership (in Framingham MA).
I appreciate the info you posted here back on March 22nd 2013 about the harmonic balancer but this document seems to govern 2009-2012 Corvettes. I just had my balancer replaced (56K mikes) and this one appears to be at least as bad as the unit Chevrolet removed. Also this one is wobbling in the vertical plain as well. Do you, or anyone else, know what the spec is for the 2006 Corvette? My dealer admits they are short of information but agrees this one is really wobbling but's not replacing it without run out specs.
Any help would be appreciated!
Originally Posted by Gene Culley
GM actually has specs on it. My Camaro SS was making this noise terribly at the end of the summer and I had to replace it.
#PIP4750E: Belt Squeak Noise And/Or Crankshaft Balancer Appears To Wobble - (Feb 10, 2012)
Subject: Belt Squeak Noise and/or Crankshaft Balancer Appears to Wobble
Models: 2010-2012 Chevrolet Camaro SS
2011-2012 Chevrolet Caprice
2009-2012 Chevrolet Corvette
2008-2009 Pontiac G8
with 6.0L 6.2L Engine (RPOs L76 L77 L99, LS3, or LS7)
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some customers may complain of a belt squeak noise and/or a crankshaft balancer appears to be out of balance or wobbling while watching it with the engine running. In most cases, the wobble is an optical illusion because the design of the balancer gives the appearance that it is moving more than it actually is.
Recommendation/Instructions:
If this concern is experienced, follow the steps below:
1. Push the crankshaft all the way to the rear of the engine.
2. Using a magnetic base, attach a dial indicator so the measuring tip is contacting the rear of the drive belt groove.
Notice: An inaccurate reading may be obtained by measuring the face of the balancer instead of the rear of the drive belt groove.
3. Rotate the crankshaft 360 degrees and note the total amount of crankshaft balancer run out.
◦If the balancer run out is 0.40mm (0.0157”) or less, do not replace the balancer because the run out is in specification.
◦If the balancer run out is greater than 0.40mm, replace the crankshaft balancer and perform step 3 again to confirm that the run out of the new balancer is in specification.
4. If the customer has complained of a belt squeak, also replace the drive belt.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
03-22-2013, 04:05 PM
Any "spec" on harmonic balancer run-out
Pretty much.
