Powerflex purple diff bushes - replace rear only?

There are several threads about poly bushes for the diff and the ones I've read have many questions not answered.

I was torn between black (95A) or purple (80A) powerflex bushes for the diff. For awareness, I am changing the rear subframe bushes to TMS ally.

I've settled on the purple because I do not want diff whine and some owners have mentioned a small increase with the black series. If anyone has any vids with the black series diff bushes pls post.

Questions
1 - is anyone running the purple diff bushes and is there an increase in diff whine?

2 - given the rear bush is foam and the other 2 harder rubber. Is there a need to replace more than the foam bush?

3 - If anyone has installed Malek's (MRF) diff damper, pls chime in if it resolved diff whine with solid / delrin diff bushes?

Thanks.

I just bought AKG red for the subframe and black for the diff. $410 shipped from Pelican. Not in the car yet so no feedback. Based on comments about diff whine, I went with black instead of red for the diff. This is supposed to be my comfortable car.

I had both TMS solid subframe bushing + powerflex diff bushing (purple). I replaced all 3 diff bushing along with the subframe work.

It has a bit whine from the diff now - all is came from the Diff bushing. The whine sound level is somewhat depends on your rpm, speed & throttle degree. To me it is not too loud and most of the time the whine is covered by my Akra exhaust. Personality I like the diff whine sound.

testdriver wrote

I had both TMS solid subframe bushing + powerflex diff bushing (purple). I replaced all 3 diff bushing along with the subframe work.

It has a bit whine from the diff now - all is came from the Diff bushing. The whine sound level is somewhat depends on your rpm, speed & throttle degree. To me it is not too loud and most of the time the whine is covered by my Akra exhaust. Personality I like the diff whine sound.

Hmmm, I was not expecting the purples to produce diff whine - damm!

Another forum member messaged me as he was running the black series diff bushes and said there was whine at constant rpm at motorway / highway speeds but it was only just noticeable. His partner did not even notice.

Are you able to post a video with the whine pls?

pbonsalb wrote

I just bought AKG red for the subframe and black for the diff. $410 shipped from Pelican. Not in the car yet so no feedback. Based on comments about diff whine, I went with black instead of red for the diff. This is supposed to be my comfortable car.

Your feedback on the powerflex black would be appreciated.

When do you expect to get the install done?

Probably in a month. Just need a free weekend.

I installed the purple diff bushings and solid aluminum subframe bushings. I only hear the diff whine from 55-60 mph. I do have an Akrapovic Evo exhaust that most likely masks some of the whine.

burnrbr wrote

I installed the purple diff bushings and solid aluminum subframe bushings. I only hear the diff whine from 55-60 mph. I do have an Akrapovic Evo exhaust that most likely masks some of the whine.

Hi. Did you install all 3 bushes? So the diff whine range is very narrow. Is your car manual or DCT. I believe the whine is more pronounced with DCT cars. My stock car has a little diff whine at certain speeds, most people would not notice. My previous manual car did not.

Ant Man wrote

Hi. Did you install all 3 bushes? So the diff whine range is very narrow. Is your car manual or DCT. I believe the whine is more pronounced with DCT cars. My stock car has a little diff whine at certain speeds, most people would not notice. My previous manual car did not.

I installed all three purple bushings. My car is a DCT and yes the noticeable whine is only 55-60 mph.

burnrbr wrote

I installed all three purple bushings. My car is a DCT and yes the noticeable whine is only 55-60 mph.

Do you think the poly diff bushings made a difference in addition to solid subframe bushings?

edwardgtxy wrote

Do you think the poly diff bushings made a difference in addition to solid subframe bushings?

If you're referencing the whine, I did both that the same time so I can't directly comment.

The research I've read on this forum indicates that if you don't won't any whine then only do one not both. If you want to protect your diff from broken bolts, then upgrade those bushings. If you want a more planted rear suspension and less wheel hop, then replace the sub frame bushings. Doing both sub frame and diff bushings will result in some whine being heard inside the car. If you do solid diff bushing and solid sub frame bushings you'll get a lot of whine all of the time. I went the route of the softer poly diff bushings to reduce the whine which was successful. I'm not supercharged, so the "basic" poly bushings are more than enough for my situation. I've seen stock M3 break their diff bolts and tear up their sub frame mounts. It's not a situation I want to be in. I choose the solid sub frame bushing for improved rear end feel that I've read about. I'm generally happy with my choices, but it would have been great to have no whine and all benefit.

Good thread!
Going with Solid + Powerflex Purple!

Do we really need a harder diff bushing with DCT??
I have yet to see broken diff bolts on a DCT car. Has this happened lately?
.

aus wrote

Do we really need a harder diff bushing with DCT??
I have yet to see broken diff bolts on a DCT car. Has this happened lately?
.

I think it's more that if you're already taking the subframe down to do the subframe bushings, that's the right time to also do the diff bushings.

I am planning on Solid + purple sometime down the road. DD + HPDE.

Anyone go yellow?

I have the MRF solid subframe bushings. I believe he used derlin diff bushings from turner. The whine is minimal, and can only be heard with the windows up.

What are these "softer poly bushings" some have mentioned? Are they talking about the purple ones or is there another brand?

Powerflex purple is probably the softest. I bought akg black but not installed yet.

pbonsalb wrote  

Powerflex purple is probably the softest. I bought akg black but not installed yet.

I did black as well, still a significant amount of noise.

I currently have solid aluminum subframe bushings. I previously had Delrin diff bushings but recently replaced them with PowerFlex purple diff bushings. I also have the differential damper that MRF recommends installed on the car, which was also on the car for some of the time I had the Delrin bushings.

I have a DCT car.

My thoughts are as follows:

1) The subframe bushings absolutely transform the rear end of the car, IMO. It is more noticeable the harder you drive and push the car.

2) For me, the Delrin differential bushings added a significant and noticeable amount of differential whine. It was most present when cruising on the highway. I found it annoying. I also noticed some knocking and clunking from the driveline when putting the car into reverse, neutral, or drive. I did not find this particularly annoying.

3) The differential damper took a bit of the whine out (maybe 10%), but resulted in a fairly significant (>50%) reduction in the knocking/clunking.

4) The switch to PowerFlex purple differential bushings reduced probably another 90-95% of the differential whine to the point where I honestly no longer hear it even with the windows up and the radio off. Maybe in that scenario, if you absolutely strain to listen for it, you might catch the faintest whine at the perfect speed for a quick moment. And even then, that would only be true if you knew what you were looking for, which 99% of you will not.

5) In terms of performance, I perceive almost no difference in performance between the Delrin and poly diff bushings. If there is, it is slight, maybe 10%. This leads me to believe that 90% of the improvement in the rear-end feel is from the subframe bushings and that the differential bushings are mostly icing on the cake.


TL;DR:

Solid aluminum subframe bushings paired with PowerFlex purple differential bushings give you at least 90% of the performance benefits of a full solid setup, but with no more than 10% of the noise associated with a full solid setup.

Hujan wrote  

I currently have solid aluminum subframe bushings. I previously had Delrin diff bushings but recently replaced them with PowerFlex purple diff bushings. I also have the differential damper that MRF recommends installed on the car, which was also on the car for some of the time I had the Delrin bushings.

I have a DCT car.

My thoughts are as follows:

1) The subframe bushings absolutely transform the rear end of the car, IMO. It is more noticeable the harder you drive and push the car.

2) For me, the Delrin differential bushings added a significant and noticeable amount of differential whine. It was most present when cruising on the highway. I found it annoying. I also noticed some knocking and clunking from the driveline when putting the car into reverse, neutral, or drive. I did not find this particularly annoying.

3) The differential damper took a bit of the whine out (maybe 10%), but resulted in a fairly significant (>50%) reduction in the knocking/clunking.

4) The switch to PowerFlex purple differential bushings reduced probably another 90-95% of the differential whine to the point where I honestly no longer hear it even with the windows up and the radio off. Maybe in that scenario, if you absolutely strain to listen for it, you might catch the faintest whine at the perfect speed for a quick moment. And even then, that would only be true if you knew what you were looking for, which 99% of you will not.

5) In terms of performance, I perceive almost no difference in performance between the Delrin and poly diff bushings. If there is, it is slight, maybe 10%. This leads me to believe that 90% of the improvement in the rear-end feel is from the subframe bushings and that the differential bushings are mostly icing on the cake.


TL;DR:

Solid aluminum subframe bushings paired with PowerFlex purple differential bushings give you at least 90% of the performance benefits of a full solid setup, but with no more than 10% of the noise associated with a full solid setup.

Hm. I may pull my AKG black and give the purples a whirl. Hopefully it gets rid of some of my whirl. See what I did there? Lol

Where can I find this diff damper? I did a search yielded no results. It's not the defiv diff brace correct?

Move Over wrote

Hm. I may pull my AKG black and give the purples a whirl. Hopefully it gets rid of some of my whirl. See what I did there? Lol

Where can I find this diff damper? I did a search yielded no results. It's not the defiv diff brace correct?

+1

What's the diff damper??

Are there PowerFlex poly rear sub-frame bushings available. If yes, has anyone compared them to aluminum?
Great info here.
.