I'm sure there is a spec. I had to try to look it up, though. The most helpful I found was this:
I say that's helpful because it seems that these things just inherently wobble and that comment was from someone that sees a lot and agrees. You could yeet $80 at it and replace it and the bolt. But, I wouldn't worry about it unless it gets worse or bad enough to make to make the belt chirp.
*EDIT*
Found
a spec:
#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)
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This PI was superseded to update recommended field. Please discard PIP4750D.
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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.
