Poly mounts and excess engine vibration

KenH

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I installed the Woodhouse poly engine mounts (black) and Dave's poly trans mount and billet crossmember.

At idle there is a little more vibration to the car which I was expecting. At about 2000 rpm there is a significant engine vibration. Bad enough that it feels like I'm running on 9 cylinders or something. It starts to smooth back out as the RPMs increase. The vibration is also there with the clutch in and the engine rev'd to around 2000 rpms.

Anyone else experience this? Is this amount of vibration to be expected? I read all the posts on this topic and no one mentions having additional vibration when under power after the install, only a little more at idle.

On the trans mount, I used the extra plate under the mount per the directions that came with it, but it did seem like the stackup height was a little higher than the stock mount. I ruled this out as the issue due to the vibration being there with the clutch in. I also checked the plug wires and made sure that they were still seated.

Next step will be to check the balancer and then pull the trans mount back out and replace with stock. I REALLY don't want to have to swap the stock engine mounts back in if at all possible. That's one job I don't want to have to do twice.
 

ViperTony

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I installed the Woodhouse poly engine mounts (black) and Dave's poly trans mount and billet crossmember.

At idle there is a little more vibration to the car which I was expecting. At about 2000 rpm there is a significant engine vibration. Bad enough that it feels like I'm running on 9 cylinders or something. It starts to smooth back out as the RPMs increase. The vibration is also there with the clutch in and the engine rev'd to around 2000 rpms.

Anyone else experience this? Is this amount of vibration to be expected? I read all the posts on this topic and no one mentions having additional vibration when under power after the install, only a little more at idle.

On the trans mount, I used the extra plate under the mount per the directions that came with it, but it did seem like the stackup height was a little higher than the stock mount. I ruled this out as the issue due to the vibration being there with the clutch in. I also checked the plug wires and made sure that they were still seated.

Next step will be to check the balancer and then pull the trans mount back out and replace with stock. I REALLY don't want to have to swap the stock engine mounts back in if at all possible. That's one job I don't want to have to do twice.

I have/had vibration with the same set of mounts when I initially installed them. I was warned by Woodhouse I would get more vibration from these mounts compared to the OEM. It's been 2000 miles since I installed them. In fact, I liked the vibration and car feels stronger. I don't even notice it anymore.
 

dave6666

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If you are running on 9 cylinders then shoot your headers with an IR thermometer. The cold one is to blame.

Or like Tony said. Get used to it.

I've got an off road car with metal to metal frame mounts engine and tranny. Poly is like Cadillacin'.
 
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KenH

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So... what you guys are saying is to man up :D

I put in a cold weather tune and went out and beat on it a bit. Car is running strong, so no missing cylinders. The vibration seemed to be less today and a more reasonable level, so either I am already getting used to it or the mounts just needed a few full power runs to break them in a bit.
 

VIPER GTSR 91

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My Woodhouse Red mounts did the same thing for a couple hundred miles but has smoothed out since. I really noticed a difference at the track. Hope you get it solved.
 

ViperRay

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I have the same motor and tranny mounts and no vibration here.
Of course, the whole car now rocks back and forth at idle ('97 GTS) instead of the engine but I like it and it made a significant difference at the track.
 
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KenH

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I have to say that it is pretty impressive that I can gun the engine with the hood open and the engine doesn't move a bit. With the stock mounts, it would torque over quit a bit. The shifter also stays planted.

As others have noted, it does seem like the power is a little more immediate when the throttle is hit. Overall, the car feels a little more solid.
 

dave6666

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I have to say that it is pretty impressive that I can gun the engine with the hood open and the engine doesn't move a bit. With the stock mounts, it would torque over quit a bit. The shifter also stays planted.

As others have noted, it does seem like the power is a little more immediate when the throttle is hit. Overall, the car feels a little more solid.

You are now man too.

But seriously, one helluva change from rubber - maybe worn out rubber - mounts, to new poly.

Great post though. They are a drastic change from stock, and your experience is worth reading. I've done the tranny, gonna do the engine when I put my new headers on, but feel qualified to rant because of the afore mentioned off road car. Rubber, or even hard poly, beats the crap out of metal chassis to metal engine!
 

dave6666

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KenH

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The instructions shipped with Dave's mount said that the extra plate must be used as it is not a spacer, but an upper preload plate. Not sure if the same is true of the other mounts.
 
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DAMN YANKEE

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Dave...now Dave....I didn't write that one......its much better than any of mine.
 
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From my contact with the engine and transmission mount customers the vibrations do calm down a little with a few miles. This may also be psychosomatic and they are just "tuning" them out! I love the difference also because the car is so much more responsive to throttle inputs.
Thanks for all your support!
 

ViperTony

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My vibrations went away. I don't notice them anymore and they were quite evident at idle. So much so that my rearview mirror kept sliding down from the vibrations and I had to constantly adjust it. It's normal now. Give it a little time.

As for the spacer plate on the trans poly mount: When I originally did the write up I stated not to use the spacer plate per Dave's Big Brakes instructions. We thought the plate would interfere with the height of the transmission and affect the shifter since the new poly mount is slightly taller than the stock OEM. It turns out the spacer plate is needed in order to pre-load the mount. It doesn't interfere with the shifting as initially we initially thought. I need to modify the how-to to include the spacer plate.
 
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powerstream

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KenH or others,
how long does it take to install these items

Thanks
 
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KenH

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KenH or others,
how long does it take to install these items

Thanks

This is one of those things that seems to take longer than it should. You are limited as to how high you can easily raise the motor and it's a tight fit. The engine mounts take some monkeying to get them out, then back in and then lined up between the frame and the engine. Kind of like a puzzle trying to get those things in and out around the exhaust. I wasn't feeling well, so split the install up over two days, but probably took me 3-4 hours total to do what seemed to be 1 hour worth of actual work.

The trans mount is a snap and can be done in less than an hour.

This was with Belanger headers on the car. Might be easier (or harder) with the stock exhaust manifolds. Someone else posted that they cut off a little of the extra stud length and that would probably make installation of the new mounts easier.
 

TexasPettey

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I installed my Woodhouse poly mounts about a year ago. It was easy, 2 hrs tops. That included raising and lowering the car. There is some more vibration, but I don't think it's extreme. I went from a Gen1 cam to a 708 cam after the install. With the more agressive cam, the vibration is more noticable. However, I think they are well worth it. The only place I really feel the vibration is in the steering wheel at idle.
 

Purdue_Boiler_Viper

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I have the same motor and tranny mounts and no vibration here.
Of course, the whole car now rocks back and forth at idle ('97 GTS) instead of the engine but I like it and it made a significant difference at the track.

Yeah baby! A rockin GTS. I'm ordering mine today. :D
 

Purdue_Boiler_Viper

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I installed the Woodhouse poly engine mounts (black) and Dave's poly trans mount and billet crossmember.

At idle there is a little more vibration to the car which I was expecting. At about 2000 rpm there is a significant engine vibration. Bad enough that it feels like I'm running on 9 cylinders or something. It starts to smooth back out as the RPMs increase. The vibration is also there with the clutch in and the engine rev'd to around 2000 rpms.

Anyone else experience this? Is this amount of vibration to be expected? I read all the posts on this topic and no one mentions having additional vibration when under power after the install, only a little more at idle.

On the trans mount, I used the extra plate under the mount per the directions that came with it, but it did seem like the stackup height was a little higher than the stock mount. I ruled this out as the issue due to the vibration being there with the clutch in. I also checked the plug wires and made sure that they were still seated.

Next step will be to check the balancer and then pull the trans mount back out and replace with stock. I REALLY don't want to have to swap the stock engine mounts back in if at all possible. That's one job I don't want to have to do twice.

I'm reviving this because I had somewhat the same experience as Ken. I didn't feel vibration as much as heard weird noises from the transmission area, even with the clutch in. Sometimes the noise was loud enough to be somewhat alarming. I had zero noise before the install.

When I installed Dave's mount and crossmember, I noted that it clearly raised the tranmission higher than stock. I wondered if I had made a mistake in the install, and there was some interference, so I pulled off the stone shield and looked carefully. I did not find any interference, so I decided to take off the mount and inspect it. When I got it off, I measured Dave's stackup vs. stock, and found that Dave's was going to raise the transmission higher than stock by the thickness of the preload spacer.

Given that the motor mounts were solid as a rock, and the noise was coming from the transmission area, I decided to leave out the spacer and see what happened with the noise. It is completely gone now.

I did a Belanger header install along with the mounts. I'll continue to monitor the car to see if the noise returns.
 

EllowViper

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The starter really "hits" with the poly mounts too. I noticed that right away. I have the aforementioned vibrations, but I got used to it. I really notice it in the mirrors.
 

dave6666

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Although I haven't road tested yet - in the middle of that exhaust mod - I did start the car Friday night since it was enough back together to hear and see the fruits of my labor. I had also just put in Woodhouse black mounts.

The engine used to rumble around at idle. The doors would wiggle a bit at idle when they were open. Remember that post I did about driveline vibration at high speed that was so bad it felt wrong, like slow down wrong? Rock steady now at idle, and I'll bet my 2009 drinking budget the driveline vibration will be gone.

So it may be a matter of where your starting point is... Me? Car was coming apart. Me now? Still need the the road test, but I'll bet a little humming will feel just sweet compared to before.

And sorry to keep posting this, but my old DS mount...

You must be registered for see images
 

Qualitywires.com

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Make sure the mounts are aligned right and the tranny is not angled weird. I installed some on an SRT and it didn't vibrate at all. I have a write up here somewhere on this site.
 

Purdue_Boiler_Viper

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Make sure the mounts are aligned right and the tranny is not angled weird. I installed some on an SRT and it didn't vibrate at all. I have a write up here somewhere on this site.

The mounts are dead on the original marks. The strange thing is I didn't have vibrations at all. Only rattles / clunks.

Did I mention the car is strong as HELL! Don't get me started on the exhaust leaks. But, once I got them sorted out with some gaskets, I am stoked. :D
 

ViperTony

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The mounts are dead on the original marks. The strange thing is I didn't have vibrations at all. Only rattles / clunks.

Did I mention the car is strong as HELL! Don't get me started on the exhaust leaks. But, once I got them sorted out with some gaskets, I am stoked. :D


I had vibration early on but its gone. I don't know if this was the solution but I leveled my engine after installing the mounts. I forget which side it was but I had to shimmy one of the mounts about 1/4" to get the engine level. I haven't had any issues with the poly trans mount but I'm not using that spacer plate for it. I have no idea if that makes any difference with drivetrain vibration.
 

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