Poly Differential Bushings

[Exclusivs]

There appears to be 2 companies who offer Polyurethane differential bushings for the E9X's; Powerflex & AKG. Looking for feedback from those who have gone this route vs solid or derlin. The latter 2 do not seem a viable option on what still remains my daily driver.

Powerflex is produced in one of three durometers:
yellow (70A – stiffer than rubber), purple (80A), and black (95A – very stiff)

AKG looks to offer two options:
red (75D- recommended race application), and black (95A)

Do Polyurethane bushings require "maintenance" or develop noise?

[CIFUM3]

Oh man did a quick research and derlin bushings and seems like it's NOT the way to go! Haha (I was curious about them) That being said I want the poly ones but need some reviews also ^^

Bump

[pbonsalb]

I am going to use AKG poly diff and subframe bushings. Have not decided yet on 95A or 75D. Might put 75D in one location and 95A in another. 75D is close to delrin.

I run AKG 95A diff bushings in my turbo 99M3 with Powerflex 80A subframe bushings and noticed no NVH increase. So I will go stiffer for the E90M3.

[flipm3]

Originally Posted by Exclusivs

There appears to be 2 companies who offer Polyurethane differential bushings for the E9X's; Powerflex & AKG. Looking for feedback from those who have gone this route vs solid or derlin. The latter 2 do not seem a viable option on what still remains my daily driver.

Powerflex is produced in one of three durometers:
yellow (70A – stiffer than rubber), purple (80A), and black (95A – very stiff)

AKG looks to offer two options:
red (75D- recommended race application), and black (95A)

Do Polyurethane bushings require "maintenance" or develop noise?

I have yet to use the AKG stuff on my E90 M3, but I've used them on a lot of E46 and E36s. Always been a great experience.

With the poly differential bushings, maintenance shouldn't really be necessary. I would expect a slight increase in whine, but certainly not as drastic as solid aluminum or delrin.

Originally Posted by pbonsalb

I am going to use AKG poly diff and subframe bushings. Have not decided yet on 95A or 75D. Might put 75D in one location and 95A in another. 75D is close to delrin.

I run AKG 95A diff bushings in my turbo 99M3 with Powerflex 80A subframe bushings and noticed no NVH increase. So I will go stiffer for the E90M3.

I will be going a similar route. My plan is to go 95A in the diff and possibly solid in the subframe.

[bdaddylo]

Originally Posted by pbonsalb

I am going to use AKG poly diff and subframe bushings. Have not decided yet on 95A or 75D. Might put 75D in one location and 95A in another. 75D is close to delrin.

I run AKG 95A diff bushings in my turbo 99M3 with Powerflex 80A subframe bushings and noticed no NVH increase. So I will go stiffer for the E90M3.

Any updates?

[Shredicus]

Just ordered some 95a akg poly diff bushings that I'm going to have installed with my solid subframe bushings. Will report back on nvh.

[Hujan]

Originally Posted by Shredicus

Just ordered some 95a akg poly diff bushings that I'm going to have installed with my solid subframe bushings. Will report back on nvh.

Please do. Also: DCT or 6MT?

[sk2613]

just installed the akg street version, small increase in whine and firmer over expansion joints on bridges. but def feels better and rear doesn't shimmy. worth it.

[Hujan]

Originally Posted by sk2613

just installed the akg street version, small increase in whine and firmer over expansion joints on bridges. but def feels better and rear doesn't shimmy. worth it.

Are you on the stock subframe bushings?

[e92zero]

Originally Posted by sk2613

just installed the akg street version, small increase in whine and firmer over expansion joints on bridges. but def feels better and rear doesn't shimmy. worth it.

I am assuming you installed all 3? Did you DIY or pay a shop to do it? Powerflex sell the front 2 and the rear 1 separately. Wondering since only the rear one is foam if we can just replace the rear one with poly and that will be enough to help while not adding any nvh. Thoughts?

[checkmate]

Sub'd

For the sake of good order, can you guys post up the specific manufacturer + part # on this thread. This should be useful for future reference.

[wrecklessfool]

Originally Posted by e92zero

I am assuming you installed all 3? Did you DIY or pay a shop to do it? Powerflex sell the front 2 and the rear 1 separately. Wondering since only the rear one is foam if we can just replace the rear one with poly and that will be enough to help while not adding any nvh. Thoughts?

The firm bushing out back with the softer rubber up front may not be a good thing. My logic is it would be the same as adding delrin engine mounts with stock trans mounts. Not advisable. One provides some flex and movement while the other is much more rigid. Might just transfer the bolt shearing issue to the front diff bolts. I guess it came be thought of as the same logic as to why the rear bolt snaps?

[e92zero]

Originally Posted by wrecklessfool

The firm bushing out back with the softer rubber up front may not be a good thing. My logic is it would be the same as adding delrin engine mounts with stock trans mounts. Not advisable. One provides some flex and movement while the other is much more rigid. Might just transfer the bolt shearing issue to the front diff bolts. I guess it came be thought of as the same logic as to why the rear bolt snaps?

^I see. Thanks. Do we have cases of the rear bolt snapping? All the ones I have seen have been the front bolt breaking and the thought is the rear foam allow for too much movement. The front bolts are 12mm and the rear one is 14mm. I just thought that if both Powerflex and ECS offer just the rear one by itsef (even though the ECS one seems to be wrong), it might be okay to just upgrade that one.

[wrecklessfool]

Originally Posted by e92zero

^I see. Thanks. Do we have cases of the rear bolt snapping? All the ones I have seen have been the front bolt breaking and the thought is the rear foam allow for too much movement. The front bolts are 12mm and the rear one is 14mm. I just thought that if both Powerflex and ECS offer just the rear one by itsef (even though the ECS one seems to be wrong), it might be okay to just upgrade that one.

Actually, I think you're right about the front bolts breaking. Never had that issue myself as I replaced all my bushings within 3k miles of owning my car.

I believe the same logic applies as I stated above, though. The stress will have to be transferred elsewhere once the solid bushing is installed. I guess without engineering analysis it's hard to say what might happen. Maybe this is the magic formula though?

[ashtaron14]

I had Powerflex Purple Diff Bushings and Turner Subframe Mounts installed together.

There's a lot of low speed clink clank clunks, especially in start stop traffic. In speeds above 70km or so there would be a whine/whistle that begins.

The car's rear def. feels more planted, and the trade-off for the noise isn't too bad.

[sk2613]

Originally Posted by Hujan

Are you on the stock subframe bushings?

got the subframe bushing changed as well.

[sk2613]

Originally Posted by e92zero

I am assuming you installed all 3? Did you DIY or pay a shop to do it? Powerflex sell the front 2 and the rear 1 separately. Wondering since only the rear one is foam if we can just replace the rear one with poly and that will be enough to help while not adding any nvh. Thoughts?

had a shop (Rogue Engineering in NJ) do the install. not sure about only replacing the rear. honestly, it's only slightly noticeable vs. stock. however, i don't daily the car, so am happy with the tradeoff.

[Hujan]

Originally Posted by sk2613

got the subframe bushing changed as well.

What subframe bushings did you use? Solid aluminum, Delrin, or poly?

Sorry for all the questions.

[sk2613]

Originally Posted by Hujan

What subframe bushings did you use? Solid aluminum, Delrin, or poly?

Sorry for all the questions.

akg street version.

[Ant Man]

[QUOTE=ashtaron14;17392261]

I had Powerflex Purple Diff Bushings and Turner Subframe Mounts installed together.

There's a lot of low speed clink clank clunks, especially in start stop traffic. In speeds above 70km or so there would be a whine/whistle that begins.
QUOTE]

That's odd as several other owners on this site with the poly bushed diff and solid subframe bushes have said there are no additional noises. I wonder if your installer tightened up the subrame to the body properly?

Would you be able to post up a video of the noises pls? I'm looking to install the same items but do not want to suffer from clunking noises.

[kitw]

I found the whine of Delrin diff bushings to be intolerable. The subframe bushings made a huge difference and trivial NVH by themselves. I would do the subframe bushings first - you can always go back and do diff bushings later (they don't require dropping the subframe to do)

[dereksM3]

So Powerflex Purple is 80A and AKG street is 95A?

Interesting part is one member reports very little added NVH with the 95A diff bushings and the other with 80A Powerflex reports more clinks/clack NVH. Both have solid subframe bushings.

The variable could be fricition modifiers in the differential unit. Doesn't the newer fluid have higher friction modifiers to quiet the rear diff down? Maybe some of the added NVH from the older style fluid is magnified with any amount of stiffer bushings?

I'm curious as I would like to do the Powerflex with hopefully little added NVH. The subframe bushings can wait since those would have to have the subframe dropped.