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      12-28-2013, 03:01 AM   #45
aajami
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Quote:
Originally Posted by Malek@MRF View Post
No need to be skeptical, however I do understand where it stems from. For years it has been preached that Solid S/F bushings will increase NVH, but this has also come greatly from hearsay and was never true. Intuitively we would also think that NVH will increase since rubber is being removed and replaced with forged Aluminum, however that is not true. The front S/F is also solid mounted to the chassis and this unit deals with engine vibration as well as well as suspension loads.

Yes, changing the differential bushings to solid will increase some noise, but not "vibration" or "harshness". There is no reason for vibration to increase as the differential that has been unitized is not vibrating, unless something is out of balancing with the half shafts or propeller shaft itself creating harmonic vibration.
Hi Malek,

What are your thoughts on changing the subframe bushings but keeping the stock differential bushing intact for street driving? Any increase in noise, especially a whine, is going to be off-putting.
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      12-30-2013, 01:52 PM   #46
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Quote:
Originally Posted by aajami View Post
Hi Malek,

What are your thoughts on changing the subframe bushings but keeping the stock differential bushing intact for street driving? Any increase in noise, especially a whine, is going to be off-putting.
I have done this for a few cars now. It is an excellent upgrade without exhibiting any form of NVH or whine from the differential. I can 100% guarantee that changing the S/F bushings will not increase NVH by any noticeable or measurable degree.

One of my customers, Pertplus opted for this route, and much like you, he wanted the car to be setup correctly, perform well and provide rear end stability without NVH as the car is only street driven.

The sub-frame bushings provide the following benefits:
- zero deflection of the frame
- zero possibility of tearing the mounts
- maintains alignment geometry, since the frame cannot shift laterally or longitudinally.
- increased traction
- more power applied to the wheels (energy transfer efficiency is increased)
- drastically reduced wheel hop (wheel hop can be eliminated when combined with the differential bushings as well as changing out the lower control arm bushings)
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      12-30-2013, 03:25 PM   #47
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Quote:
Originally Posted by Malek@MRF View Post
- drastically reduced wheel hop (wheel hop can be eliminated when combined with the differential bushings as well as changing out the lower control arm bushings)
Like these?

http://www.dinancars.com/products/M-...oball-Kit.aspx

Also, out of curiosity, you talked about the drawbacks of replacing the differential bushings, but what are the benefits of doing so for a DCT car? The benefits of the subframe bushings seem obvious to me, but what should we be looking for with the differential bushings?
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      12-30-2013, 04:17 PM   #48
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Quote:
Originally Posted by Malek@MRF View Post
I have done this for a few cars now. It is an excellent upgrade without exhibiting any form of NVH or whine from the differential. I can 100% guarantee that changing the S/F bushings will not increase NVH by any noticeable or measurable degree.

One of my customers, Pertplus opted for this route, and much like you, he wanted the car to be setup correctly, perform well and provide rear end stability without NVH as the car is only street driven.

The sub-frame bushings provide the following benefits:
- zero deflection of the frame
- zero possibility of tearing the mounts
- maintains alignment geometry, since the frame cannot shift laterally or longitudinally.
- increased traction
- more power applied to the wheels (energy transfer efficiency is increased)
- drastically reduced wheel hop (wheel hop can be eliminated when combined with the differential bushings as well as changing out the lower control arm bushings)
Thanks for the response, Malek. Is there a noticeable difference in the feel of the suspension at all with just the change to the subframe bushings during (admittedly aggressive) street driving.
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      12-30-2013, 06:43 PM   #49
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Quote:
Originally Posted by Hujan View Post
Like these?

http://www.dinancars.com/products/M-...oball-Kit.aspx

Also, out of curiosity, you talked about the drawbacks of replacing the differential bushings, but what are the benefits of doing so for a DCT car? The benefits of the subframe bushings seem obvious to me, but what should we be looking for with the differential bushings?
No, those are for the front control arms, those are not for the rear lower camber arm. However those arms you linked provide a great benefit to steering input and correcting a lot of the problems associated with lowered vehicles and very wide front wheel/tire setups.

The benefit of the differential bushings is snappier control of the rear end power and application. Less deflection of the differential means better control and improved traction. The factory differential has 2 forward mounts and a offset single mount on the rear. This design inherently leads itself to deflecting on the passenger side very aggressively to the point of catastrophic hardware failure.

Quote:
Originally Posted by aajami View Post
Thanks for the response, Malek. Is there a noticeable difference in the feel of the suspension at all with just the change to the subframe bushings during (admittedly aggressive) street driving.
Aside from a massive improvement in power delivery, greater traction, less wheel hop and a more consistent alignment, there is no change in comfort. If we want to gauge it by "feel" it is quite hard to verbally explain any other way.. It simply feels right, solid and planted. Feel of suspension will not change. The springs and dampers will behave similarly, except the rear springs and shocks will be working more accurately as the sub-frame can no longer move and manipulate and affect the spring and shock (both of those items are affected if the sub-frame deflects/moves).

I hope this answers your questions a little better.
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      12-31-2013, 12:40 AM   #50
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^^^^^^ what he said! I love how my car drives with the bushings.
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      12-31-2013, 03:04 AM   #51
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Quote:
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^^^^^^ what he said! I love how my car drives with the bushings.
Is your drivetrain or engine modified in any way?
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      12-31-2013, 09:10 AM   #52
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Quote:
Originally Posted by aajami
Quote:
Originally Posted by Pertplus View Post
^^^^^^ what he said! I love how my car drives with the bushings.
Is your drivetrain or engine modified in any way?
I have a ESS VT2-585 supercharger
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      12-31-2013, 04:47 PM   #53
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Quote:
Originally Posted by Pertplus View Post
I have a ESS VT2-585 supercharger
Thanks. Curious to find someone whose done the solid subframe mod who doesn't have a stroker or a supercharger.
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      12-31-2013, 07:01 PM   #54
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Quote:
Originally Posted by aajami
Quote:
Originally Posted by Pertplus View Post
I have a ESS VT2-585 supercharger
Thanks. Curious to find someone whose done the solid subframe mod who doesn't have a stroker or a supercharger.
I have done the subframe and diff mounts, and love the way the rear end stays planted. My review is somewhere on the forum with pics.
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      01-01-2014, 12:46 AM   #55
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This is an invaluable thread for those of us that want to keep our M3s forever.

Malek, I see two different options for the differential mounts at Turner, will the all delrin setup provide more comfort?

Also, can you post the exact labor cost (minus parts) to do the subframe and differential bushings?

Also, how much extra labor to do motor mounts?

Last edited by Leonardo629; 01-01-2014 at 04:58 PM.
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      01-03-2014, 11:50 AM   #56
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Yeah, you will probably not get any sound with the power flex stuff.
I was surprised, and impressed, that powerflex offers so much for the E9xM3 platform.
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      01-03-2014, 01:19 PM   #57
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I was surprised, and impressed, that powerflex offers so much for the E9xM3 platform.
They have a big line of stuff. I have Poly sway bar bushings on my E36 and the one downside is they squeak if I don't keep them lubed.
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      01-03-2014, 05:51 PM   #58
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For a more DD application could you recommend the Powerflex bushings Malek (more so just the differential for NVH purposes)? Say for a car making 400whp or less. I feel in my DCT it almost has drivetrain slop, you let of the gas too fast at low speeds and theres almost clunks and too much wheel hop for a car of this caliber.
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      04-27-2014, 11:11 PM   #59
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With access to a lift, how much time is required to change the diff bushings? There's a tech day coming up @ one of the local BMW shops, and I'd like to DIM (Do It Myself) if it is 2hrs or less.
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      04-28-2014, 01:04 PM   #60
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Quote:
Originally Posted by whats77inaname View Post
With access to a lift, how much time is required to change the diff bushings? There's a tech day coming up @ one of the local BMW shops, and I'd like to DIM (Do It Myself) if it is 2hrs or less.

Unfortunately you will no be able to do the diff bushings as a DIY in less than 2 hours.
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      04-28-2014, 01:16 PM   #61
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Quote:
Originally Posted by Malek@MRF View Post
Unfortunately you will no be able to do the diff bushings as a DIY in less than 2 hours.
How long does it take you guys to get it done?
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      04-28-2014, 02:01 PM   #62
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Quote:
Originally Posted by whats77inaname View Post
How long does it take you guys to get it done?
Differential bushings take about 3-3.5 hours. Exhaust, differential, shielding paneling all need to be removed as well. Subframe needs to be slightly lowered to allow for the tooling to get in there.
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