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      02-23-2018, 09:36 PM   #1
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Smile Solid Diff Mounts

Going to drop my diff soon for a 4.10 ratio swap.

Might as well give it a birthday party with some new diff mounts/bushings. Just ordered a set from Turner HERE

Anyone tried running solid aluminium mounts on their diff?

Should really tighten things up a bit compared to OEM and they are then maintenance free, never have to touch them again.

Plenty of E46 guys have done it and they say the NVH is negligible.

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      02-24-2018, 12:44 AM   #2
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Quote:
Originally Posted by ANILE8 View Post
Going to drop my diff soon for a 4.10 ratio swap.

Might as well give it a birthday party with some new diff mounts/bushings. Just ordered a set from Turner HERE

Anyone tried running solid aluminium mounts on their diff?

Should really tighten things up a bit compared to OEM and they are then maintenance free, never have to touch them again.

Plenty of E46 guys have done it and they say the NVH is negligible.

Well let's see (hear)! I had hard (80 durometer) poly for awhile and it transformed my car into car tractor (sound wise). Interested!
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      02-28-2018, 04:28 AM   #3
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I wouldn't say that then there is no maintenance mate, those vibes go somewhere, and that somewhere is where you fill find extra maintenance to do. But, do let us know how you find it. Interested in your feedback.
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      02-28-2018, 04:44 AM   #4
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I will indeed report back after the install.

If you research the E46 subframe issues and broken diff support brackets you might be surprised to find that actually the opposite is true.

It is suggested by those who know far more than I, that the factory flexible rubber mounts are responsible for causing the damage in the first place, solid mounts actually reduce mechanical stress.

If you like axle tramp and wheel hop stick with the standard rubber bushings
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      02-28-2018, 07:24 AM   #5
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Quote:
Originally Posted by Finnegan View Post
Well let's see (hear)! I had hard (80 durometer) poly for awhile and it transformed my car into car tractor (sound wise). Interested!
Are you sure they were shore80A?

Shore80A is usually the 'soft' polyurethane like the purple powerflex or red strongflex. Shore90A, shore95A or even stiffer is considered 'hard' (but nowhere near as hard as solid aluminium or Delrin).
But shore80A is usually stiffer than the stock rubber, expecially when thats already a few years old (thats then more like shore70a although there are various stiffnesses in a car)

I have shore80A as diffmounts and subframe mounts and have no whine etc what so ever. But I did choose shore80A over shore90A (which I put in most parts of the rest of my suspension) partly because of potential whine in those spots.

Quote:
Originally Posted by ANILE8 View Post
solid mounts actually reduce mechanical stress.
Thats not possible from a technical pov imho. But that doesnt automatically means that solid mounts will cause problems.
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      02-28-2018, 05:23 PM   #6
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Quote:
Originally Posted by ANILE8 View Post
Plenty of E46 guys have done it and they say the NVH is negligible.
Friend did it in his E46 M3 and mentioned the NVH increase was bothersome - primarily a street car. He promptly removed them. Your mileage may vary depending on car use and tolerance for NVH.


I have the Rogue Engineering engine and transmission mounts and the slight increase in NVH was noticeable but I am OCD.
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      03-01-2018, 01:47 AM   #7
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Quote:
Originally Posted by GuidoK View Post
Quote:
Originally Posted by Finnegan View Post
Well let's see (hear)! I had hard (80 durometer) poly for awhile and it transformed my car into car tractor (sound wise). Interested!
Are you sure they were shore80A?

Shore80A is usually the 'soft' polyurethane like the purple powerflex or red strongflex. Shore90A, shore95A or even stiffer is considered 'hard' (but nowhere near as hard as solid aluminium or Delrin).
But shore80A is usually stiffer than the stock rubber, expecially when thats already a few years old (thats then more like shore70a although there are various stiffnesses in a car)

I have shore80A as diffmounts and subframe mounts and have no whine etc what so ever. But I did choose shore80A over shore90A (which I put in most parts of the rest of my suspension) partly because of potential whine in those spots.

Quote:
Originally Posted by ANILE8 View Post
solid mounts actually reduce mechanical stress.
Thats not possible from a technical pov imho. But that doesnt automatically means that solid mounts will cause problems.
It was long ago so I could have the durometer wrong. The resulting resonance frequency was just unpleasant.
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      03-01-2018, 11:56 AM   #8
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am i the only one that doesn't know what NVH stands for...
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      03-01-2018, 12:40 PM   #9
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Quote:
Originally Posted by knowthebattle View Post
am i the only one that doesn't know what NVH stands for...
Noises Vibration Harshness
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      03-02-2018, 10:14 PM   #10
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Quote:
Originally Posted by knowthebattle View Post
am i the only one that doesn't know what NVH stands for...
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      03-03-2018, 09:49 AM   #11
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Anyone installed these? How is the NVH compared to stock and how did it improve the driving experience?
Performance Polyurethane Differential Bushing:
ES#: 2748535
ES#: 2748537

https://www.ecstuning.com/b-ecs-part...002447ecs01~a/

Product Details

Your rear differential is indirectly connected to your right foot through the engine and driveline, and connected to the seat of your pants through the chassis. Soft factory rubber differential bushings absorb vibrations between chassis and differential, providing comfort and softness in both of these connections.
Enter ECS Tuning's In-House Engineered Performance Polyurethane Differential Bushings. By eliminating the deflection factory rubber bushings permit, the connection between your right foot (and your seat) to the wheels is improved. Removal of this slop allows for crisper power transfer from differential to wheels, which means better throttle control while carving a canyon road, drag racing, sliding the rear end out, or just driving to work. This is achieved without the harshness or vibration associated with delrin or solid differential mounts.
Featuring a tough 88A durometer polyurethane and Black anodized 6061-T6 aluminum Sleeve, our Performance Polyurethane Differential Bushings are more resistant to chemicals, ozone degradation, road salt, and general wear and tear than factory rubber bushings, resulting in a longer service life.
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      03-04-2018, 03:56 AM   #12
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Quote:
Originally Posted by Rekla View Post
Anyone installed these? How is the NVH compared to stock and how did it improve the driving experience?
Performance Polyurethane Differential Bushing:
ES#: 2748535
ES#: 2748537

https://www.ecstuning.com/b-ecs-part...002447ecs01~a/

Product Details

Your rear differential is indirectly connected to your right foot through the engine and driveline, and connected to the seat of your pants through the chassis. Soft factory rubber differential bushings absorb vibrations between chassis and differential, providing comfort and softness in both of these connections.
Enter ECS Tuning's In-House Engineered Performance Polyurethane Differential Bushings. By eliminating the deflection factory rubber bushings permit, the connection between your right foot (and your seat) to the wheels is improved. Removal of this slop allows for crisper power transfer from differential to wheels, which means better throttle control while carving a canyon road, drag racing, sliding the rear end out, or just driving to work. This is achieved without the harshness or vibration associated with delrin or solid differential mounts.
Featuring a tough 88A durometer polyurethane and Black anodized 6061-T6 aluminum Sleeve, our Performance Polyurethane Differential Bushings are more resistant to chemicals, ozone degradation, road salt, and general wear and tear than factory rubber bushings, resulting in a longer service life.
I have the 80 version on my subframe. No real NVH increase. https://powerflexusa.com/howtochoose.aspx
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      03-04-2018, 08:01 AM   #13
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Quote:
Originally Posted by Finnegan View Post
I have the 80 version on my subframe. No real NVH increase. https://powerflexusa.com/howtochoose.aspx
Subframe is not usually a problem, you can go completely solid alum. and not get NVH.
......as long as you still have some isolation on the sub-components.

BMW is now running solid subframes on GTS etc.

I'm installing solids on my M3 subframe with powerflex purple on the diff, so I guess I'll soon find out first hand :
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      03-04-2018, 08:16 AM   #14
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Quote:
Originally Posted by inTgr8r View Post
BMW is now running solid subframes on GTS etc.
Yes but if you look at the base of the f82 subframe its about twice as wide as that from our cars. Its not a matter of NVH in the GTS, but a matter of forces.
The narrower the base of the subframe, the bigger the twisting forces. Twice the width, half the force
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      03-04-2018, 10:24 AM   #15
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Quote:
Originally Posted by GuidoK View Post
Yes but if you look at the base of the f82 subframe its about twice as wide as that from our cars. Its not a matter of NVH in the GTS, but a matter of forces.
The narrower the base of the subframe, the bigger the twisting forces. Twice the width, half the force
Interesting... I see what your saying, that definitely makes sense.

In the case of the narrower subframe with more twisting forces,
would it not be more beneficial to use solid bushings to minimize forces on the chassis and impart them more directly to the wheels?
(subframe & chassis become unitized)
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      03-04-2018, 11:30 AM   #16
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Quote:
Originally Posted by Finnegan View Post
I have the 80 version on my subframe. No real NVH increase. https://powerflexusa.com/howtochoose.aspx
Do you know what OE is on that chart?
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      03-04-2018, 02:07 PM   #17
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Quote:
Originally Posted by inTgr8r View Post

In the case of the narrower subframe with more twisting forces,
would it not be more beneficial to use solid bushings to minimize forces on the chassis and impart them more directly to the wheels?
(subframe & chassis become unitized)
The more solid the connection, the higher the peak forces.
Any kind of dampening reduces peak forces and dissipates the total amount of energy over a longer timespan.
So the softer the bushings, the lower the stress on the chassibolts and chassis itself (mainly the spotwelds). And the wider the chassisbolts/mounts, the more area it has to dissipate energy and the lower the lever forces.

I dont know if its a real problem with the z4 but with the e46 its a major problem. Although that has also to do with a design flaw. With the z4 the rear subframe sits in a full cage (the rear tension/pull rods enclose both the petrol tank and the subframe) and with the e46 the subframe sits in a C section (the tension/pullrods dont enclose the rear subframe, just the petrol tank).
But however you look at it, the subframe is much much stronger than the chassis so it can tear it up without any doubt.

It obviously also has to do with what kind of mileage you expect from your car. If you do 2k miles/year and you expect to keep the car for another 5 years it wont be as much of a problem (20k miles), but usually a car is designed to last 200k miles or so without major disasters.

you can also look at the front axle. The subframe from the fornt axle is bolted directly into the chassis, but again that subframe is twice the width if not more.
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Last edited by GuidoK; 03-04-2018 at 02:13 PM..
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      03-04-2018, 02:27 PM   #18
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Thanks, thats interesting!

I was aware of the E46 issues.
The Z3 also had subframe problems
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      03-04-2018, 02:38 PM   #19
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I think if you want a stiffer rear setup its better to use stiffer bushings in the control arms.
First of all compression/expanding of those bushings has more effect on wheel geometry, and secondly if something in that department fails its much easier to repair. Just swap out cheap parts. Repair welding on chassis is much more expensive and its not always apparant where the damage sits.

Look at the youtube video's redish motorsport puts up. They specialize in the e46 chassis and know it by heart to the spotweld where some of the problem areas are and that often means cutting out whole panels to get to certain enclosed box sections where internal damage sits. With the z4 chassis.... no one has that experience and if something goes wrong in that department you can be chasing that problem for years, cutting the whole car apart panel by panel.



This video gives you an idea why you want to prevent damage to the body at any cost... The damage you see with your eye is only part of the story.
Its the main reason why all my polyurethane bushings that directly touch the body arent stiffer than shore80a
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Last edited by GuidoK; 03-04-2018 at 02:47 PM..
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      03-04-2018, 04:20 PM   #20
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Thank you GuidoK for sharing all of this - very interesting. I'm sticking with the OEM rear diff bushings for now!
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      03-05-2018, 01:30 AM   #21
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Quote:
Originally Posted by XMetal View Post
Quote:
Originally Posted by Finnegan View Post
I have the 80 version on my subframe. No real NVH increase. https://powerflexusa.com/howtochoose.aspx
Do you know what OE is on that chart?
About 60 if the 80 are 30% more than stock.
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      03-06-2018, 10:19 AM   #22
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Quote:
Originally Posted by GuidoK View Post
Look at the youtube video's redish motorsport puts up. They specialize in the e46 chassis and know it by heart to the spotweld where some of the problem areas are and that often means cutting out whole panels to get to certain enclosed box sections where internal damage sits.
This is a problem that plagues a lot of E46's. There are aftermarket solutions, but it requires cutting and welding. If it isn't already cracked, there is a solution involving some very expensive structural epoxy. I was worried my son's 330Ci would have this issue, but we got lucky, and his car just made the cut to get the factory reinforcement. BMW installed a plastic block and epoxied it between some panels to eliminate the amount of flex beginning on 2005 model.

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