Mounts
03-25-2012, 11:07 AM
#1
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Mounts Just replaced my motor mounts yesterday and wow, what a difference. Fixed the startup clunk and idle shifting into 1st gear clunk. I used the creative steel mounts. Only small issue I notice is there is some vibration at idle and where I used to be able to kinda roll out of first gear with the clutch now I need to rev it up a little more or it vibrates pretty rough. This only happens at 1000 or below.
I have the diff mount and trans mount as well, I was just wondering if any of you guys changed it out with the diff in the car without the CS puller that they rent out? Dont want to lower the diff to fight that thing for hours if you all already have another solution.
Thanks! Looking forward to getting rid of that damn rear clunk
I have the diff mount and trans mount as well, I was just wondering if any of you guys changed it out with the diff in the car without the CS puller that they rent out? Dont want to lower the diff to fight that thing for hours if you all already have another solution.
Thanks! Looking forward to getting rid of that damn rear clunk
03-25-2012, 11:16 AM
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Well... Those urethane mounts are a lot more solid than the stock mush mounts so it's normal to feel that after the change. I'm running UMI solid mounts and i've noticed some added vibration but honestly, it's way worth it to know my motor is bolted down solid and tight and I'll never have to worry about it again! 
GL with the rear diff bushing. Sure someone here will have a suggestion on how u can do it without fighting it for hours.
GL with the rear diff bushing. Sure someone here will have a suggestion on how u can do it without fighting it for hours.
03-26-2012, 09:50 AM
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Did putting in the stock trans mount with the new enigne mounts help with the vibrations? I just did all three and am getting some vibs, but think some of it is due to bad flywheel, should know soon with new LS7 flywheel and clutch. Right around 2200.
Pulling my CS diff bushing out as I am putting a G-Force 9" in once it shows up.
Pulling my CS diff bushing out as I am putting a G-Force 9" in once it shows up.
03-26-2012, 12:20 PM
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Did putting in the stock trans mount with the new enigne mounts help with the vibrations? I just did all three and am getting some vibs, but think some of it is due to bad flywheel, should know soon with new LS7 flywheel and clutch. Right around 2200.
Pulling my CS diff bushing out as I am putting a G-Force 9" in once it shows up.
Pulling my CS diff bushing out as I am putting a G-Force 9" in once it shows up.
Honestly, I don't think the changing the clutch out is going to make one bit of difference. Seems like most people who have installed motor mounts get this same vibration, and I believe it is just a result of the oscillation characteristics of the engine running at 2200-ish RPM's combined with the natural harmonics of the chassis. I'm all for somebody proving me wrong on this though, so please report back after the clutch swap.
03-26-2012, 01:09 PM
#7
I think you guys with might want to take a peek at your harmonic balancer. According to the owner of Thunder Racing (his LS6 CTS-V with 60k miles apparently does the 1/4 in 10.6 with only a cam and a spring kit) claims that the OEM motor mount material and dampening material in the OEM harmonic balancer are one and the same.
He further theorized that they tend to crap out at about the time, which causes the motor vibrate dangerously, which is masked by the shot engine mounts. The really scary part is that people wrongly attribute the engine shaking to the shot motor mounts instead of the bad harmonic balancer. Most people ignore the balancer until it begins shredding belts, which is way too late to avoid major internal damage due to harmonic resonance in the crank slamming moving parts past fluid barriers and causing very high frequency metal-on-metal contact.
He further theorized that they tend to crap out at about the time, which causes the motor vibrate dangerously, which is masked by the shot engine mounts. The really scary part is that people wrongly attribute the engine shaking to the shot motor mounts instead of the bad harmonic balancer. Most people ignore the balancer until it begins shredding belts, which is way too late to avoid major internal damage due to harmonic resonance in the crank slamming moving parts past fluid barriers and causing very high frequency metal-on-metal contact.
Last edited by FuzzyLog1c; 03-26-2012 at 01:22 PM.
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03-26-2012, 02:11 PM
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I am going to check the balancer. I had horribly bad mounts, one leaking fluid(pass side) and the other was almost as bad, but couldnt completely spin it in itself. Also put a G-Force 2 piece drive shaft in at the same time (along with a whole slew of other parts) and was getting some noise/ vibs from it. Pulled out and double checked slip yoke oreintation, was good so I turned it 180 via tans and diff, fixed most of vibs but still some noise. Problem for me is I think the bad muonts were masking another problem, which is one reason why I am doing the clutch.
I guess I can just run the motor with d/s and exhaust off and check the balancer.
Has the vibration at 2200 been noticed and corrected with a balancer?
I guess I can just run the motor with d/s and exhaust off and check the balancer.
Has the vibration at 2200 been noticed and corrected with a balancer?
03-26-2012, 02:50 PM
#9
I don't know enough to tell you that. My V only has 22k miles, most of which have been gentle. My OEM balancer and motor mounts are fine, but that's going to change with the cam and blower that are going in. This falls under the category of preventative maintenance.
03-26-2012, 03:50 PM
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03-26-2012, 04:32 PM
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I got a brand new balancer, didn't help the vibes. Now, a dealer tech installed it, and considering they f*cked up every install they touched, it could be held on there with 75 ft lbs of torque for all I know.
Last edited by Cadzilla; 03-26-2012 at 04:41 PM.
03-26-2012, 04:33 PM
#14
Absolutely. Every time a cylinder fires, your crankshaft is deflected slightly. There is a resonant point and several characteristic harmonics. Instead of me trying to explain it, check out the following articles on ATI's site. I know that they also sell dampers, but these are solid articles written by engineers.
http://www.atiracing.com/products/dampers/101/index.htm
http://www.atiracing.com/products/da...ting/index.htm
http://www.atiracing.com/products/da...mper_dinan.htm
To quote this guy:
Did they replace your original one with another OEM balancer, or did you upgrade to something that's suitable for the level of power that you're putting out?
Most OEM dampers are simply rigid wheels with a thin layer of rubber sandwiched somewhere in there--they're almost useless.
Edit: one more article. Very tech heavy. The most important part of the article:
http://www.popularhotrodding.com/eng...or2/index.html
http://www.atiracing.com/products/dampers/101/index.htm
http://www.atiracing.com/products/da...ting/index.htm
http://www.atiracing.com/products/da...mper_dinan.htm
To quote this guy:
With high horse power/high rpm applications utilizing a ATI damper large hp gains are not uncommon being that timing accuracy is greatly improved due to reducing crankshaft torsional twisting that would be transmitted to camshaft and ignition timing inaccuracies.
Another advantage of a proper damper would be greatly reducing stress to the crank shaft, bearings and oil pump gears reducing the chances of mechanical failures. This has been proved time and time again on any serious build race engines.
Another advantage of a proper damper would be greatly reducing stress to the crank shaft, bearings and oil pump gears reducing the chances of mechanical failures. This has been proved time and time again on any serious build race engines.
Most OEM dampers are simply rigid wheels with a thin layer of rubber sandwiched somewhere in there--they're almost useless.
Edit: one more article. Very tech heavy. The most important part of the article:
"Within the industry it is generally accepted that a typical V-8 can, at what appears to be the most important third and fourth order harmonics, tolerate about 0.4 of a Degree Double Amplitude (+/- 0.2 of a degree) almost indefinitely. These third and fourth order harmonics also seem to be the ones that have the greatest adverse effect on power. The object of the exercise then is to damp crank vibrations to something below this 0.4 DDA threshold.
Last edited by FuzzyLog1c; 03-26-2012 at 04:51 PM.
03-26-2012, 06:26 PM
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I suppose it's possible that this could be a harmonic balancer issue. And it probably IS in some cases. It just seems to me though, that too many people, of widely varying vehicle age, mod level, and driving history, exhibit very very similar vibration behavior after installing the solid mounts. I have a hard time believing that the harmonic balancer is the primary culprit in all of those cases.
The only horsepower related mods I presently have done to my car are an intake and exhaust, and it only has 38k miles on it. So I have an even harder time pointing my finger at a "faulty" harmonic balancer as the cause in my case.
Now is it entirely possible that the OEM balancer design is inadequate to a certain degree, and it's lack of dampening capability is masked by the OEM motor mounts? Sure. I'd buy that any day. It would certainly explain the widespread occurrence of similar vibration "issues". I put issues in quotes because honestly, the degree to which one would consider the vibrations a problem varies from person to person. They don't bother me one bit. Ill be standing by my engine vibration/RPM/chassis harmonics theory until somebody switches to an aftermarket balancer and reports that the vibes are no more.
The only horsepower related mods I presently have done to my car are an intake and exhaust, and it only has 38k miles on it. So I have an even harder time pointing my finger at a "faulty" harmonic balancer as the cause in my case.
Now is it entirely possible that the OEM balancer design is inadequate to a certain degree, and it's lack of dampening capability is masked by the OEM motor mounts? Sure. I'd buy that any day. It would certainly explain the widespread occurrence of similar vibration "issues". I put issues in quotes because honestly, the degree to which one would consider the vibrations a problem varies from person to person. They don't bother me one bit. Ill be standing by my engine vibration/RPM/chassis harmonics theory until somebody switches to an aftermarket balancer and reports that the vibes are no more.
03-26-2012, 06:38 PM
#16
Well, when I get the UMI mounts (waiting for them to have another sale), I'll let you know if I have any vibration issues. I owe this forum a huge build summary post with pictures after all of the help I've gotten over the last year.
03-26-2012, 07:42 PM
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Awesome.. I'll be lookin forward to it!
11-05-2012, 02:34 PM
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So outta curiosity what was the outcome on all this?
