A quick followup... I have discovered something VERY interesting! The part number I was given by my dealer was GM12635652. Apparently, GM Canada has ZERO inventory of this part. So I phone a dealer in Ogdensburg NY and I was quoted $230US (less than half the price quoted by my dealer - given our dollar's parity with the US this is really annoying but I digress) and guess what - GM US has ZERO inventory of this part as well!!
This is highly suspect given that the LS2 is used in a host of vehicles including the Pontiac GTO, a number of Holden (Australia) vehicles, Cadillac CTS-V, Trailblazer and even Saab. So, either there has been a rash of repairs which has depleted inventory or GM has pulled the part off of it's shelves in order to assess their early failures. In either case this gives hope for a GM hidden warranty.
B.
Suspicious indeed ! The only other possible scenario I can add to it's unavailability is possibly the part is mfg'd in Japan and the supply chain is temporarily broken...
That being said, I have a speculative theory on the early and widespread failure of the part.
Based on multiple internet references from many LS2 model specific forums, the first time people notice the "balancer wobble" is when the car develops the telltale "chirping". Then, while investigating the source of the "chirp" they notice the infamous "Wobbling Crankshaft Balancer". Those who take it to the dealer for diagnosis usually end-up with a belt replacement that temporarily eliminates the "chirping" for a month or so. This "Drive Belt Chirping Diagnosis" diagnostic & repair procedure is spelled-out in vol. 2, page 6-45 of the Tech Manual.
I have also found a few anecdotal references online of switching the belts to Goodyear Gatorbacks and eliminating the problem permanently. So, this weekend I opted to experiment with the Gatorback belt replacement and this is what I found.
Based on the Tech Manual "chirping" diagnosis procedure #3, it is recommended to remove both belts and operate the engine for 30-40 seconds to determine if the chirp is eliminated. So, prior to removing the OEM belts I "scored" the face of the outer and inner mechanisms and put a dab of white paint on the rubber bushing. Then I measured the runout of the outer mechanism "balancer / pulley" at 800 RPM idle. The runout was appx. 2 mm while the inner mechanism was zero. And the "chirping" sound was still present.
I then removed the belts, started the engine and repeated the measurement with a result of appx. 4.5 mm runout on the outer mechanism and again zero on the inner. The "chirping" was eliminated completely. This was an increase of 2.5 mm's of "wobble" just by removing the OEM belts and letting the Crankshaft Balancer spin free at 800 RPM.
I then installed the Goodyear Gatorback belts which are much beefier belts than the OEM and fit much snugger than the OEM belts which had 32,500 miles on them. This is probably due to wear and stretching over the years.
Again, I fired-up the engine checked the dash for a CEL or SES light and listened for the "chirping". Thankfully it had gone. Then I examined the pulleys and belts to make sure they were seated properly and while doing so, noticed a decrease in the balancer "wobble". I measured it again and the "wobble" had been reduced to appx. 1 mm only. And almost looked like a solid crankshaft balancer.
This got me thinking about the design and assembly of the balancer and what effects tightly vs. loosely fitting belts would have on the bonding and tensile strength of the rubber bushing between the rubber to metal mechanisms.
My hypothesis is that as the OEM belts age, they stretch slowly which progressively lessens the pull / stiffness on the Crankshaft Balancer assembly. This allows the outer mechanism to float or shift on the rubber bushing due to centrifugal / torsional forces causing the rubber to soften / flex and the metal to rubber bonding to weaken from constant movement thus allowing the balancer to "wobble" which as it worsens, causes the chirping belts which eventually leads us to discover the "wobbling" balancer.
In conclusion, If the OEM belts were replaced before they stretched to the point of allowing the balancer to shift on it's rubber bushing, would this prevent the ultimate failure of the Crankshaft Balancer Assembly.
Perhaps GM should install belts that are a bit less likely to stretch in such a short period of time, or they should require the belts be changed at regular scheduled maintenance intervals before the loosened belts allow enough play for the Balancer to start softening the rubber bushing and it's bonding agent. Because I believe when the balancer gets to the point of having enough runout "wobble" to cause the belts to chirp, it has gotten to an inevitable failure state.
