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2010 Cadillac CTS-V
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268 Posts
Discussion Starter · #1 ·
I have been looking to see if the LS6 is internally or externally balanced. I had a clutch / flywheel installed yesterday and I am getting a vibration at 1800 rpm up. This is in neutral with clutch in or out, so it made me think the flywheel i put in was out of balance.

After reading posts on here of simular problems, I found where it says our engines are externally balanced in the shop manual. Well that doesn't make since to me as the balancers don't use a woodruff key or anything to keep then in the same position on the crank. They can be installed on the crank at any rotation point.

So my question is which is it turely, Internal or External? This will make a huge difference on fixing my vibration issue.

Thanks, Jeff
 

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2005 CTS-V
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8,363 Posts
It is externally balanced. The instructions on removing and replacing the harmonic balance tell you to mark the location and return it to its original position.
 

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2010 Cadillac CTS-V
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268 Posts
Discussion Starter · #3 ·
Well, I looked at the ATi damper install instructions and they don't mention anything about marking, moving weights or getting balanced. Also, the only ones I can find to purchase say they are for internal balance, CTS-V specific part number. Does anyone know the factory part number for our cars?
 

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2005 CTS-V
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8,363 Posts
I show an OEM Part number for the LS6 of 12560115. The instruction to mark the balancer is only appicable to the factory installed balancer, which was used to acheive the original external balance.

Once you move away from the original flywheel and clutch, as many of us have done, the original external balance is lost. I am not sure what the process is to get back in balance if you are unlucky with a replacement clutch. (I was lucky with my replacement flywheel).

Perhaps those who have installed after market balancers will chime with information as whether those units can be weighted to cure an out of balance condition.
 

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2010 Cadillac CTS-V
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268 Posts
Discussion Starter · #6 ·
Well, I have been talking to some people trying to figure out the issue I am having with a vibration after a clutch/flywheel install and here is what I have been told.

Katech - Internally Balanced
ATi Dampers - Internally Balanced
True Steet Performance (local shop) - Internally Balanced

I also read somewhere there that flywheels balanced neutral for internally balanced engines and what they refered to as "Detroit Balanced" for externally balanced engines.

Anyone have any info on changing their balancer or flywheel and having a vibration at 1800 rpm reving it up in neutral and how they fixed.

Also, a clutch vendor said they had seen the vibration problem occure when a flywheel was installed and the bolts were used to pull the flywheel on the crank. Material gets in the way of a flush fit. Said you need to pull back off clean off any galling, heat to expand the center hole and reinstall. Made sense to me. This wasn't my issue, they supect the clutch itself is bad and we are replacing it.
 

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04 CTS-V with a little hp persuasion device
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They are internally balanced. If it were externally balanced, it would have a balancer like this. Also they flywheel will be weighted. Our balancer is actually just a harmonic dampener, not a balancer. The internal rotating assembly is balanced and then theoretically when you bolt neutral balanced parts to it, you should be good to go. However; everything has tolerances and if you get a flywheel that is just on the edge and bolt to an engine that is just on the edge and get them phased incorrectly (just a craps shoot) then you can have some undesirable results. You can probably start rotating parts until you get a smooth rotating assembly because eventually you should find a phase that cancels each other out. Hence the whole indexing of the driveshaft for vibrations. FWIW I had a few vibes with both my LS7 and my SPEC stage junk and now that I have the Exedy, its nice and smooth.



 

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2005 CTS-V
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8,363 Posts
They are internally balanced. If it were externally balanced, it would have a balancer like this. Also they flywheel will be weighted. Our balancer is actually just a harmonic dampener, not a balancer. The internal rotating assembly is balanced and then theoretically when you bolt neutral balanced parts to it, you should be good to go. However; everything has tolerances and if you get a flywheel that is just on the edge and bolt to an engine that is just on the edge and get them phased incorrectly (just a craps shoot) then you can have some undesirable results. You can probably start rotating parts until you get a smooth rotating assembly because eventually you should find a phase that cancels each other out. Hence the whole indexing of the driveshaft for vibrations. FWIW I had a few vibes with both my LS7 and my SPEC stage junk and now that I have the Exedy, its nice and smooth.
Well since I have never pulled my own balancer and I did not see the stock flywheel when it was removed I am cannot actually have an independent opinion on all this. The Service Maual however, does indicate that the engine is externally balanced using weights in, or on, both the stock flywheel and the stock balancer. If it comes to a vote, I will certainly vote for internally balanced, but at this point I am just confused. (But my engine isn't vibrating so....).
 

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2011 CTS-V / 2010 SRX 2.8T
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296 Posts
Having removed and replaced the stock pulley/balancer I can comment that I didn't notice any external balancing or indexing.
 

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Discussion Starter · #10 ·
Well since I have never pulled my own balancer and I did see not the stock flywheel when it was removed I am cannot actually have an independent opinion on all this. The Service Maual however, does indicate that the engine is externally balanced using weights in, or on, both the stock flywheel and the stock balancer. If it comes to a vote, I will certainly vote for internally balanced, but at this point I am just confused. (But my engine isn't vibrating so....).
I laughed out loud on that vibration comment!

I had installed a UUC flywheel and CTS-V clutch with no vibration before also. It figures to me is all these things are neutral then they should all not vibrate, less the ones with the heat and install issue I described before.

My install was done by an excellant LS guy and he didn't have to heat as the flywheel, went on without any interfearance from the crank. We pulled it all back apart and there was no scrapes and there was a uniform ring around the flywheel showing that it was pulled up tight to the crank. Everyone is now thinking that it was the clutch causing this issue. According to the place I got it, the clutch (factrory GM) has been the cause of this issue in 2 of the 100ish kits they have sold.

I will let everyone know the outcome this weekend after we get the new clutch and it is installed.
 

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2005 Black CTS-v
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5 Posts
Hey Jeff,

Did the new clutch resolve your issues? I'm going through a similar problem right now and am having a hard time getting resolution. I did the LS7 clutch swap last July and have had high frequency vibrations accompanied by a high-pitched ring (almost like those little bells you'd have a on bicycle, but at a higher frequency.) I had the clutch and pressure plate zero-balanced last week, however, it did nothing to fix the issue.

It's getting a bit discouraging because I want to track the V but not if these vibrations are going to destroy my crank (and other) bearings.

Any update would be appreciated.

Thanks,
Matt
 

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2005 CTS-V
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8,363 Posts
Anything more ever come of this?
I'm not sure what your asking, but I have since learned that CTSV154 was correct - the engine is internally balanced. The LS7 clutch setup is notorious for causing vibrations unless balanced before installation. The vibration does reportedly decrease with usage. Other aftermarket clutch setups vary, but appear to be less vibration prone, based on reports on this forum.
 

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05 CTS-V
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69 Posts
I had my LS7 flywheel and pressure plate balanced together and installed a Fluidampr at the same time...vibes around 2500+. Replacing the damper with an OEM piece to see if that helps, if not, will be looking into a new clutch or perhaps some tricky external balancing. Unfortunately, we tossed my old balancer so I can't verify if it had index marks/weights/extra holes or not. I know the engine SHOULD be internally balanced, and probably was, but tolerance stackup is a bitch and from what I've read, some LS6s were also externally balanced before shipping. It makes sense, anyway...
 

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2007 CTS-V Black-on-Black
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I'm working at an LS shop over the summer and I just asked about this. Vibration after a clutch swap is the flywheel, and they're not always cut or balanced perfectly. It could also be the balancer at the front of the motor falling apart. There is rubber that goes first, followed by a metal ring that works its way off.
 
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