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Discussion Starter #1
For those of you who have installed full polyurethane bushings like the full kit from Figs, how is the noise, vibration and harshness?
 

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i actually didnt notice a difference. maybe a very slight one. but my car is incredibly quiet to begin with. i also have a solid rear lower knuckle bushings (figs) and solid toe and trac arms. although a lot of that stuff doesnt bother me to begin with.

if youre concerned about NVH, go with the strong flex red bushings. theyre softer than their yellow ones. i have the yellow ones. IIRC, superpro does not disclose their durometer for their poly (someone please correct if im wrong).
 

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Has anyone done the diff or subframe bushing? I'm thinking those will be the worst contributors.

The Hardrace bushings seem to be a bit more conventional. Those are harder rubber, but I don't think they make everything for the IS. I may have to get poly for a few components like the steering rack.
 

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Has anyone done the diff or subframe bushing? I'm thinking those will be the worst contributors.
I used the Figs parts for my diff (both where the "wings" off the front of the diff housing bolt to the subframe, and also the ones on the back of the diff cover. I welded in one of the Figs diff mount reinforcement plates at the same time.

Figs doesn't sell the bushings for the subframe-to-chassis, and I was unaware of StrongFlex at the time, so I filled the OEM bushings with 3M Window Weld, which is ~75-80 durometer, from what I've read.

I did the whole suspension in one shot, so I don't know how much NVH to attribute to each part... But I did poly everywhere there was rubber from Toyota, added Figs toe links and Figs Mega RLCAs that have rod-ends instead of bushings on the inboard ends.

It's not like an all-metal racecar by any means, but there is certainly more NVH than stock. For reference, I also have Bilsteins and Eibach "pro" kit.

Here is a ride-along video I recently made to demonstrate my R154 for sale. Maybe you can get a feel for the NVH in the car over my yacking:

Around 9:25, I drive over a somewhat rough section of road. You can see/hear some sub-optimal NVH characteristics through that section.

[ame]https://youtu.be/sFH-t4klvxI?t=101[/ame]
 

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i actually didnt notice a difference. m
Me too. I have sphericals everywhere and I can't hear them.

My experience with subframe and diff bushings is that you need rubber somewhere. Either at the diff or at the subframe. Diffs are loud if they can transfer vibration to the body through the subframe.
 

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(both where the "wings" off the front of the diff housing bolt to the subframe
ive always called them pinion bushings.
My experience with subframe and diff bushings is that you need rubber somewhere. Either at the diff or at the subframe. Diffs are loud if they can transfer vibration to the body through the subframe.
the only rubber on my car is the sway bar bushings. the subframe and diff bushings i have in my car are all 90 durometer poly and i didnt notice any added vibrations or noise. although i assume that poly shares far more dampening and noise suppressing characteristics over a solid bushing (rather it be delrin or aluminum). you know more about this than I, but thats just my experience. i also do not usually drive this car for more than 30 miles at a time; maybe once every two weeks if im lucky.
 

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Discussion Starter #9
Me too. I have sphericals everywhere and I can't hear them.

My experience with subframe and diff bushings is that you need rubber somewhere. Either at the diff or at the subframe. Diffs are loud if they can transfer vibration to the body through the subframe.
I have solid subframe bushings on one of my other cars but stock diff bushings and I can't hear the diff at all. Road noise, however has been increased for sure. If I had poly control arm bushings and poly bushings in the spindle it would probably be much louder.

What I don't want to do is de-Lexusize my car and turn it into a rattle box. I would have just bought a beat up evo 8 instead lol

I'm thinking strategically replacing certain bushings with poly bushings wouldn't cause much NVH. There needs to be some rubber bushings to isolate the road noise.
 

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although i assume that poly shares far more dampening and noise suppressing characteristics over a solid bushing (rather it be delrin or aluminum).
My experience is that poly is certainly more forgiving than say aluminum. So I agree with you.

I have solid subframe bushings on one of my other cars but stock diff bushings and I can't hear the diff at all. Road noise, however has been increased for sure. If I had poly control arm bushings and poly bushings in the spindle it would probably be much louder.
Maybe I wasn't clear. I'm saying if you have solid bushings in both places you'll probably drive vibrations into the chassis. As long as there's something relatively soft in there to dampen the diff vibrations, like the stock diff bushing in your example, you're probably good.
 
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