Replacing 2005 C6 Harmonic Balancer

Keith Tedford

Keith Tedford

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Apr 30, 2012
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2005 C6 1SB
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What did they do with the LS3? It's not rocket science. You need a given amount of interference fit between the balancer and the crank shaft. You would almost think that they got sloppy with their machining tolerances. There was a time when starters needed shimming. The problem turned out to be the holes in the block were being drilled all over the place. They got some accuracy built into the equipment and the problem pretty well went away. They used to have guys working full time shimming starters in the reject area. Not after that.
 
Nope, not this time. The machines that drilled the blocks were automated and the equipment or the block was moving around some during the drilling/tapping operation. ;) Quality control just wasn't a priority when the big three had the market to themselves. Once the Japanese stepped up the pace, the big three had to pull up their pants but that didn't happen until about the mid '90s. Of course, it takes a few years for the general public to realize that a better product is coming out so the tough times continued, probably to this day. Personally, I've never had a GM lemon, and I typically put 200+K miles on vehicles. Even our old COPO Chevelle was approaching 200K as well and it was like the Energizer bunny, just kept going and going. Last year at a cruise night a guy was blathering on about GM junk. Another guy piped up that he was a Toyota mechanic and that the guy should drop by the Toyota dealership and see how busy the mechanics there are doing repairs. Today, there really isn't much difference from one brand to the next. Do they still build Yugos and Ladas. They might be the exception. ;)
 
Keith Tedford said:
What did they do with the LS3? It's not rocket science. You need a given amount of interference fit between the balancer and the crank shaft. You would almost think that they got sloppy with their machining tolerances. There was a time when starters needed shimming. The problem turned out to be the holes in the block were being drilled all over the place. They got some accuracy built into the equipment and the problem pretty well went away. They used to have guys working full time shimming starters in the reject area. Not after that.
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Well, I though I heard they changed the rubber compound holding the two pieces of the harmonic balancer together and pinned the harmonic balancer to the crank but I have no sources as I couldn't find where I read this and it could all just be a load of crape. I wouldn't listen to me at all on this one.:D
 
there is no keyway on these. perhaps they need to be pinned like manny did with velocity garry's when the blower was installed. there is a kit available, seems odd not to have been done at the factory given the horsepower. when supercharging previous generation motors , a blower crank is used with an extra key. that is if it's done properly.
 
my son's 2001 z06 had the same problem. the car had 90,000 k on it at the time.
 
Thanks Manny. I saw videos with the pully wobbling and these, on the old cars at least, were bolted to the hub and not the outer ring. I've never had a problem but will keep and eye on the pulley. After all the millions of vehicles built with harmonic balancers, you would wonder at this problem cropping up now.
 
I had the same problem on mine. That was the first thing i did when i bought my car. As soon as i turned the AC on you could feel the vibration and when i looked further you could see the wobble in the pulley. I replaced mine with a UD Pulley but it sure was a lot of work just for that but it fixed the problem. I think it is a pretty common problem for the 2005-2007 c6's.
 
Hep100 said:
I had the same problem on mine. That was the first thing i did when i bought my car. As soon as i turned the AC on you could feel the vibration and when i looked further you could see the wobble in the pulley. I replaced mine with a UD Pulley but it sure was a lot of work just for that but it fixed the problem. I think it is a pretty common problem for the 2005-2007 c6's.
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It was a problem for C5 cars, and it is still a problem for all the C6's. Some 2013's have already had issues and have had to replace the balancers.
So far, I have 72,000km's on my 06, and no issues.
As per a poll performed with C6 owners, about 30% of cars have had the balancer replaced.
Rumour has it that the same balancers are being used for the C7's YIKES!!!!
:canada:
 
Laticsfan said:
If your car develops this problem is it a simple or inexpensive fix? What is the benefit of an UD pulley? Does UD stand for under drive?
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Yes Laticsfan, UD stands for underdrive pulley. If you are going to go through the trouble of replacing the OEM crank pulley, you might as well upgrade to a better quality aftermarket pulley and gain 5rwhp in the process.

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