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2005 CTS-V
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Discussion Starter #1
I have a fairly bad vibration that starts around 1500 rpms and continues all the way through the rpms. It's at it's worse at 2150 rpms. Any advice or input would be greatly appreciated.

Here is where I'm at...

2005 CTS-V with 30k miles. No performance mods except intake. No headers or aftermarket exhaust.

Doesn't matter if the car is moving or not. Doesn't matter if the clutch is engaged or not. Doesn't matter if it is in gear or not. It just vibrates all the time.

Since it vibrates in neutral standing still it eliminates drive shaft and anything else from that point back.

I just put in a LS7 clutch, Flywheel, pilot bearing, throwout, slave, etc. All new gm parts. Didn't fix it.

Took off the drive belt. Still vibrates.

I had RevShift motor mounts that were only a couple months old but I decided to check them anyway. Pulled them out and underneath the silicone heat shield one mount were melted and destroyed. Figured I found my problem. Nope. Put in new UMI motor mounts and it still vibrates. Probably worse now. Before you blame the UMI mounts, it wasn't vibrating until recently. It was perfect with the RevShift mounts for a couple months and it wasn't there before. It's not a motor mount vibration.

A couple of months ago the balancer pulley came off. I replaced it with a new GM balancer and a new ARP bolt w/ lock tite. I'm thinking this is my last place to look although its hard to believe because I just replaced it and it is not wobbling at all. But now it's burning belts. Before when I pulled the belt to test for vibration, when I put it back on it burned the belt a couple blocks away. I figured I must have put the belt on wrong. Especially when I found the burnt motor mount I figured that must have been the problem. I did the new gm belt and new UMI mount at the same time and now its squeaking and burning up the new belt. On the inside of the belt.

I'm pretty sure its the balancer at this point as a result of the belt issue. Although I don't want to pull it off unless I have to. Wondering if anyone else might have any ideas? I appreciate the advice in advance.

Tom
 

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Premium Member
2005 CTS-V
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8,363 Posts
The fact that the vibration occurs with the belt off points primarily to the harmonic balancer although it does not rule out the flywheel/pressure plate unless you had the new clutch assembly balanced as a unit prior to installation. (There is still the belt on the AC and its tensioner, but it is a less likely candidate for the cause of the vibration.)


Regarding the belt burning problem, it is possible to install the belt incorrectly such that it will appear to work, but will throw or burn belts in short order - so double check the belt routing. (see attached)

See also http://www.cadillacforums.com/forums/2004-2007-cadillac-cts-v-general/670833-vibration-feedback-through-radio.html#post13962353
 

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05 Stealth Gray V
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991 Posts
From multiple reports here, the LS6 seems to have a vibration that manifest itself between say 2100rpm and 2500 rpm. I have an 05 myself and after putting an ATI damper and a balanced LS7 clutch assembly in the car, I still have it in that RPM range. Based on removing all of the belts and replacing or balancing any other external vibration causing rotating assemblies, it would seem the vibration is coming from the engine internals and if I ever pull the motor out, I'll fix it. Until then, I'll live with it because it is better than it once was and easy to live with as it isn't that bad.

However, based on the fact that yours seems to do it throughout the rpm range, I would look towards improving it by looking at the damper and clutch assemblies. Just don't plan on eliminating it completely....
 

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2006 CTS-V
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897 Posts
Chasing vibrations in these cars is a very expensive, frustrating, and often futile effort. You've hit all the likely culprits, so no suggestions here. I do wish you luck and am curious to see any follow up though.
 

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05 maggied CTS-V, 2017 NSX Whoo Hoo!
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8,810 Posts
The burning of belts is a problem that needs to be addressed.

Since it vibrates with the engine not engaged (idle) and with the belt removed, you only have the flywheel clutch stuff and the motor (A/C may have to disconnect).

I would pull valve covers and inspect for any spring breakage/valve problem.

Maybe do compression.

You might have to pull the bell housing to inspect the clutch install.

Hope you fix it.
 

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2005 CTS-V
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Discussion Starter #6
The fact that the vibration occurs with the belt off points primarily to the harmonic balancer although it does not rule out the flywheel/pressure plate unless you had the new clutch assembly balanced as a unit prior to installation. (There is still the belt on the AC and its tensioner, but it is a less likely candidate for the cause of the vibration.)


Regarding the belt burning problem, it is possible to install the belt incorrectly such that it will appear to work, but will throw or burn belts in short order - so double check the belt routing. (see attached)

See also http://www.cadillacforums.com/forums/2004-2007-cadillac-cts-v-general/670833-vibration-feedback-through-radio.html#post13962353
You were right. I made a rookie move and had the belt routed wrong. Although now I'm leaning away from it being the balancer since it is almost new, not wobbling at all, and isn't buring belts.

Now what? Flywheel? It's just hard to believe since it was doing it before the new clutch/flywheel install. Although the stock DM was in pretty bad shape and could have been unbalanced also I guess. This car is driving me nuts.

I did take off the AC belt to rule it out and there was no difference.

Thank you everyone for your input and advice. As you see its helping. At least I figured out the belt issue.
 

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2005 CTS-V
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Given that the vibration persists with no belts, no wobbling by the balancer, and a relatively new single-mass flywheel installed, I with Heavymetals - The next investigation is to pull the valve covers and make sure the valve train (rockers, springs, and pushrods) are intact. The clutch install/balancer would follow.
 

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2004 CTS-V Blk/Blk
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785 Posts
Have you considered a misfire?

Check your plugs/wire and see what they look like. I've heard of similar problems being a broken plug wire in the past.

I would say that your problem seems unusual in that your vibration starts at 1500rpm. Most of the typical vibrations that you have addressed are normaly reported above 2000rpms.
 

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2005 CTS-V
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Discussion Starter #9
Given that the vibration persists with no belts, no wobbling by the balancer, and a relatively new single-mass flywheel installed, I with Heavymetals - The next investigation is to pull the valve covers and make sure the valve train (rockers, springs, and pushrods) are intact. The clutch install/balancer would follow.
Have you considered a misfire?

Check your plugs/wire and see what they look like. I've heard of similar problems being a broken plug wire in the past.

I would say that your problem seems unusual in that your vibration starts at 1500rpm. Most of the typical vibrations that you have addressed are normaly reported above 2000rpms.
Misfire could definitely be a possibility. I'll put it on my friends scaner, easy to check. After I'll be pulling valve covers if that's not it. Thanks guys. I'll keep you posted. Probably won't get to it until Monday or Tuesday tho.
 

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2005 Red CTS-V and a Silver 2005 CTS-V
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If you are having misfires, the check engine light would come on as the computer tracks misfires. If you find the problem, please report back. I have the same new clutch set up you have. There is pulsing from the SM flywheel that the original DM flywheel would buffer out, but that is obviously not you issue since you had it before. I am thinking of going back to a DM flywheel. I changed mine because it was not disengaging all the way making shifting a PITA. The DM flywheel in mine was definitely bad.
 

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Discussion Starter #11
If you are having misfires, the check engine light would come on as the computer tracks misfires. If you find the problem, please report back. I have the same new clutch set up you have. There is pulsing from the SM flywheel that the original DM flywheel would buffer out, but that is obviously not you issue since you had it before. I am thinking of going back to a DM flywheel. I changed mine because it was not disengaging all the way making shifting a PITA. The DM flywheel in mine was definitely bad.
So I put it up up on a lift and went through the whole car with a stethoscope and pined it down to being something in the bell housing. All mounts are now good, everything read good on my buddies computer. Took it to an engine builder friend of mine and he doesn't think its in the engine. Anyone that I've had look at it feels like it is flywheel/pressure plate related.

The only thing that explains the vibration being there before and after the clutch install is that the DM flywheel was bad and the new LS7 is bad or unbalanced also coincidentally.

So.... I'm pulling the trans back out on Thursday to inspect and send everything to a balancer and figure out whats going on. I'll let you guys know how it goes.

On a separate note I'd like to show you pictures of the RevShift motor mounts that were only a couple months old with about 1000 miles on them. They turned out not to be my problem but they were definitely a bad product that I would never use again. I sent pictures to RevShit, explained the failure, and asked for a refund. After a few weeks of ignored emails and no returned calls I finally got a hold of the owner John today and he told me that he could not refund my money but only warranty the mounts. I explained that sending a new pair would only result in the same issue because nothing had been changed. My car has stock exhaust and the mount has not changed at all. I'm not going to be putting mounts in every couple of months. I put in UMI's and they are a bit stiff but a much better mount.

The mounts looked fine on the car because the silicone heat shields was hiding the damage. It wasn't until I got them off the car and peeled the heat shield back did I see the melted/burnt area.

20150305_164049.jpg
20150305_152312.jpg
 

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Discussion Starter #12
I figured it out! Flywheel was only .5 grams off of balance, which is fine. Although once the pressure plate was bolted on it became 11 grams out of balance. Balanced the whole unit back to zero, put it all back together and vibration gone. What a relief! Thanks again for the input guys.
 

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2006 CTS-V
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Good to hear you got it figured out! What'd it cost to balance the assembly? What kinda shop does that type of work?
 

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05 Stealth Gray V
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Good to hear you got it figured out! What'd it cost to balance the assembly? What kinda shop does that type of work?
I had my ls7 kit balanced at a machine shop. Had to call around to find someone who would do it.

Mine was over 20 grams out...
 
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