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      12-20-2013, 07:19 PM   #1
JEllis
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Another solid bushing install at MRF

After six months my car is back at MRF Engineering. As I have said before, I like to do my own work. However, in this instance the work required tools, equipment and expertise that I just do not have.

I wish the weather could have been better.



I brought the beast back to MRF for something very special. About six months ago Malek and I had a discussion about the BMW OEM subframe and differential bushings. Basically, we all know the lack of rigidity in the differential bushings causes a lot of force to be placed on the differential bolt. Often these forces result in the differential bolt failing. Manual E9X M3s are especially prone to diff bolt failure.

Turner Motorsport makes solid aluminum differential bushings (at least they used to) and a solid delrin differential bolt bushing. The aluminum/delrin bushings will stabilize the differential and differential bolt against forces that could cause a failure in the mounting hardware. With the work required it made sense to also swap out the OE rubber subframe bushings for Turner Motorsport aluminum subframe bushings. Keep in mind that all new M cars and the E92 M3 GTS had solid subframe mounts. The solid subframe bushings will last forever, stabilize the suspension and protect the unibody.

As you can guess, its a lengthy and an in depth process.

GTS exhaust removed.



Exhaust, X-pip, brakes and subframe removed.



Here are all the rubber bushings removed. Notice the diff bolt bushing is actually made of foam. No wonder a lot of diff bolts fail. Removing these bushings the correct way is a very tricky process and requires some specialized tools. Malek has some very clever tools to make the removal of these bushings fast and safe.



Solid subframe bushings installed.





Differential bushings installed



All ready to go back into the car!





And finally going back in!



So how do I feel about the solid bushings! They have to be my favorite mod after the suspension and supercharger for overall feel of the car. The solid bushings help transfer power to the ground without hesitation. Essentially there is no slop or "squat" in the rear end when power is applied. The car just moves! I love the solid bushings! I highly recommend them to anyone but especially
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Last edited by JEllis; 12-20-2013 at 07:29 PM.
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      12-20-2013, 09:37 PM   #2
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Thats a lot of work to swap those out. WOW!!
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      12-21-2013, 10:51 AM   #3
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Thats a lot of work to swap those out. WOW!!
No kidding. Can they be done with the subframe in the car? As in, one bushing at a time while keeping the whole thing attached?
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      12-21-2013, 11:35 AM   #4
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^Like!^ Malek is the guy... Jellis is OK too.
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      12-21-2013, 12:11 PM   #5
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I saw those on Turner's page, but that seems like they would make the car harsh on the street. At some point I'd like to replace them, but am leaning more towards the new poly bushings. Back in my Acura days, we used to make 85A shore poly bushings ourselves for our Legends. I'm hoping that someone will make a poly diff bolt bushing to replace the foam rear diff bolt bushing, as that is just straight ridiculous.

Please report back to us in a few months and let us know if you still feel they're suitable for daily driving.
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      12-21-2013, 01:04 PM   #6
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Quote:
Originally Posted by speedaddictM3 View Post
No kidding. Can they be done with the subframe in the car? As in, one bushing at a time while keeping the whole thing attached?
In order to remove the bushings you need to have access to both sides of the subframe.

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^Like!^ Malek is the guy... Jellis is OK too.
Ha! You should come out to Big Willow on the 5th!

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Originally Posted by whats77inaname View Post
I saw those on Turner's page, but that seems like they would make the car harsh on the street. At some point I'd like to replace them, but am leaning more towards the new poly bushings. Back in my Acura days, we used to make 85A shore poly bushings ourselves for our Legends. I'm hoping that someone will make a poly diff bolt bushing to replace the foam rear diff bolt bushing, as that is just straight ridiculous.

Please report back to us in a few months and let us know if you still feel they're suitable for daily driving.
There is no harshness associated with the solid bushings. I am sure the rubber bushings absorbed a very small amount of vibration but I honestly cannot tell the difference. I drove from Yuma AZ to SoCal for the install and then drove back the same day and noticed no new harshness. The concern most people have is the sound that is transmitted to the cabin. What you get with the solid diff bushings is a little more diff sound. However, its very quiet and sometimes non existent. It sounds like roots/twin screw supercharger whine.

Anything is better than the foam diff bolt bushing that comes with the car. The solid bushings are great because I will never have to drop the subframe again. They will last forever and the mounting bolts will never have to absorb shear forces from the rubber/foam flexing under load.

Keep in mind that BMW has moved to solid subframe mounting points for all new generation M cars. The E92 M3 GTS, new M5/6 and incoming M3/4 all come with solid subframes. From what I understand the new M cars all have solid rear diff mounting points. The front mounting points are rubber while the rear point is solid.

My daily is an E36 M3 and I have some solid Turner bushing waiting for that car as well.
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      12-21-2013, 03:43 PM   #7
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Really nice work, the shop looks super clean too. With the small amount of noise that comes from the solid diff bushings, I would think the powerflex offering would help and be far better than the foam unit.
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      12-21-2013, 03:43 PM   #8
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Ha! You should come out to Big Willow on the 5th!

I might be able to do that. You planning on it?
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      12-21-2013, 04:43 PM   #9
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I might be able to do that. You planning on it?
Yeah I am signed up. The event is through speed district. I know Malek is going and I have been trying to persuade Pertplus to go as well.
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      12-21-2013, 04:44 PM   #10
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Really nice work, the shop looks super clean too. With the small amount of noise that comes from the solid diff bushings, I would think the powerflex offering would help and be far better than the foam unit.
Yeah, you will probably not get any sound with the power flex stuff.
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      12-21-2013, 07:41 PM   #11
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Quote:
Originally Posted by JEllis View Post
There is no harshness associated with the solid bushings. I am sure the rubber bushings absorbed a very small amount of vibration but I honestly cannot tell the difference. I drove from Yuma AZ to SoCal for the install and then drove back the same day and noticed no new harshness. The concern most people have is the sound that is transmitted to the cabin. What you get with the solid diff bushings is a little more diff sound. However, its very quiet and sometimes non existent. It sounds like roots/twin screw supercharger whine.

Anything is better than the foam diff bolt bushing that comes with the car. The solid bushings are great because I will never have to drop the subframe again. They will last forever and the mounting bolts will never have to absorb shear forces from the rubber/foam flexing under load.

Keep in mind that BMW has moved to solid subframe mounting points for all new generation M cars. The E92 M3 GTS, new M5/6 and incoming M3/4 all come with solid subframes. From what I understand the new M cars all have solid rear diff mounting points. The front mounting points are rubber while the rear point is solid.

My daily is an E36 M3 and I have some solid Turner bushing waiting for that car as well.
That was *totally* my bad. I was thinking of the new engine mounts that are on the market http://www.m3post.com/forums/showthread.php?t=924092

In other commentary, how long did install take?

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      12-21-2013, 07:47 PM   #12
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That was *totally* my bad. I was thinking of the new engine mounts that are on the market http://www.m3post.com/forums/showthread.php?t=924092
No worries. Solid engine and tranny mounts will be pretty harsh for daily driving. Never tried them but I imagine the sound transferred will be hard to tolerate.
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      12-21-2013, 10:55 PM   #13
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Yeah I am signed up. The event is through speed district. I know Malek is going and I have been trying to persuade Pertplus to go as well.
That sounds fun. Let me see what I can do.
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      12-22-2013, 11:19 AM   #14
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Quote:
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Quote:
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I might be able to do that. You planning on it?
Yeah I am signed up. The event is through speed district. I know Malek is going and I have been trying to persuade Pertplus to go as well.
Very convincingly I might add!!!
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      12-22-2013, 11:52 AM   #15
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Very convincingly I might add!!!
You'll enjoy it, I promise!
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      12-22-2013, 11:58 AM   #16
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Very convincingly I might add!!!
You'll enjoy it, I promise!
January 6th?
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      12-22-2013, 03:04 PM   #17
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January 6th?
5th, its a Sunday

http://www.m3post.com/forums/showthread.php?t=923098
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      12-22-2013, 07:47 PM   #18
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Yet another great solid bushing review!

Thanks for sharing. The more I read these impressions, the more I am convinced of changing my whole stigma of increased NVH with solid subframe bushings!

Quote:
Originally Posted by whats77inaname View Post
I saw those on Turner's page, but that seems like they would make the car harsh on the street. At some point I'd like to replace them, but am leaning more towards the new poly bushings. Back in my Acura days, we used to make 85A shore poly bushings ourselves for our Legends. I'm hoping that someone will make a poly diff bolt bushing to replace the foam rear diff bolt bushing, as that is just straight ridiculous.

Please report back to us in a few months and let us know if you still feel they're suitable for daily driving.
AKG Motorsport makes 95A and 75D Polyurethane Differential and Subframe Bushings.
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      12-22-2013, 11:21 PM   #19
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Yet another great solid bushing review!

Thanks for sharing. The more I read these impressions, the more I am convinced of changing my whole stigma of increased NVH with solid subframe bushings!


AKG Motorsport makes 95A and 75D Polyurethane Differential and Subframe Bushings.
Good looking out! I am DEF. going to get the 95A shore diff bushings. I'm up in the air on which subframe bushings to get, the solids or the polys. I'll have to think about that one.

Thanks again!


$140/set - http://www.akgmotorsport.com/catalog...ion%2FBushings
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      12-23-2013, 01:23 PM   #20
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Quote:
Originally Posted by flipm3 View Post
Yet another great solid bushing review!

Thanks for sharing. The more I read these impressions, the more I am convinced of changing my whole stigma of increased NVH with solid subframe bushings!


AKG Motorsport makes 95A and 75D Polyurethane Differential and Subframe Bushings.
The factory subframe bushings are about as stiff stiff as somewhere between 75D and 95A polyurethane bushings. Switching to poly bushings will not yeild the drastic benefits that are only possible with the solid aluminum bushings.

Quote:
Originally Posted by whats77inaname View Post
Good looking out! I am DEF. going to get the 95A shore diff bushings. I'm up in the air on which subframe bushings to get, the solids or the polys. I'll have to think about that one.

Thanks again!


$140/set - http://www.akgmotorsport.com/catalog...ion%2FBushings
The sub-frame should be unitized. There is no sense in the sub-frame not being directly mounted to the unibody to eliminate all axle carrier deflection.

There is ZERO NVH increase in going with solid sub-frame bushings and minimal increase in differential whine when going with solid or Delrin differential bushings.

I recommend going as stiff as possible for the differential mounts as well. I personally love the whine it makes as it sounds very mechanical and offers an audible feedback as to what the rear end is doing.
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      12-23-2013, 04:23 PM   #21
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Quote:
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The factory subframe bushings are about as stiff stiff as somewhere between 75D and 95A polyurethane bushings. Switching to poly bushings will not yeild the drastic benefits that are only possible with the solid aluminum bushings.
Wow, didn't know that BMW decided to go that stiff with stock bushings. Clearly shows the direction they're going these days comparing older generation M3s to E9X to F8X!

Thanks for the info!
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      12-24-2013, 05:52 AM   #22
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These videos are self explanatory.



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