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      11-22-2019, 02:06 PM   #133
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Quote:
Originally Posted by VictorH View Post
Purple diff bushings (wish I hadn't done that)
Would you have just replaced with OEM?
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      11-22-2019, 06:29 PM   #134
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Quote:
Originally Posted by tigermack View Post
Would you have just replaced with OEM?
YES! I drive back and forth to work on a secondary road, where speeds are all between 50-60 mph and that's exactly where the diff whine is the worst. Still a bit noisy at 70 mph but drowned out by other road noise and just not as irritating. If diff ever comes out I will replace with stock OEM bushings.
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      11-22-2019, 06:40 PM   #135
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Is it easy to replace the diff bushings without dropping the subframe? I may try putting in purples in the front 2 positions and keep the softer rear bushing stock.
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      11-22-2019, 08:00 PM   #136
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Quote:
Originally Posted by Redd View Post
Is it easy to replace the diff bushings without dropping the subframe? I may try putting in purples in the front 2 positions and keep the softer rear bushing stock.
I believe the one in the rear is the weak link, though.

Quote:
Originally Posted by VictorH View Post
YES! I drive back and forth to work on a secondary road, where speeds are all between 50-60 mph and that's exactly where the diff whine is the worst. Still a bit noisy at 70 mph but drowned out by other road noise and just not as irritating. If diff ever comes out I will replace with stock OEM bushings.
Hmm, I don't drive my car much during the week. It's mainly for the weekend but I do bring my wife and newborn around if we do take the car out... wonder if that'd be an issue.
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      11-22-2019, 11:58 PM   #137
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Rear is solid aluminum with about 3/16” of foam around it.
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      11-23-2019, 01:05 AM   #138
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I thought it's always the front ones that break?
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      01-11-2020, 02:52 AM   #139
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So I pulled the trigger and went full Powerflex Purple on the diff bushings. I had 3.45 final drive and OS Giken LSD installed at the same time, and already had solid subframe bushings installed. I was also on a lighter break-in 75-140w diff fluid fill when this test was done. Car is a daily-driven DCT with a super loud fully de-catted exhaust. So your mileage may vary.

The bad news - OK, there's definitely diff whine. I can definitely hear it, even over my super load exhaust and radio on. There's a softer high pitch whine (like a supercharger) between 30-40mph. It goes away at 40mph, and is then replaced by a lower pitch - but slightly louder - hum between 70-80mph. Sounds a lot like if you're running noisy semi-slick tires on the road. Not sure if heavier diff oil will help reduce some of the sounds but I doubt it. The whine is actually worse at initial deceleration. You might be cruising along with no noise, lift off, and the decel hum appears. There also seems to be a slight bit more driveline vibration felt in the cabin at certain rpms. Feels a bit like an exhaust pipe vibrating against the car chassis.

The good news - No diff whine above 85mph. Above this speed it sounds/feels like before. This is important as 85+mph is my usual cruising speed. Also, while I can definitely hear the whine, for some reason it doesn't bother me. Maybe cos I'm so used to my car being noisy that I just filter it out automatically. Barely 50kms of driving done and the diff whine has already blended into the cacophony of background noise. Or maybe I'm just going deaf.

So, I don't regret getting the powerflex purple diff bushes but you should seriously reconsider if you are concerned about noise.

Last edited by Redd; 01-11-2020 at 10:27 AM..
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      01-11-2020, 10:14 AM   #140
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Quote:
Originally Posted by Redd View Post
So I pulled the trigger and went full front Powerflex Purple on the diff bushings. I had 3.45 final drive and OS Giken LSD installed at the same time, and already had solid subframe bushings installed. I was also on a lighter break-in 75-140w diff fluid fill when this test was done. Car is a daily-driven DCT with a super loud fully de-catted exhaust. So your mileage may vary.

The bad news - OK, there's definitely diff whine. I can definitely hear it, even over my super load exhaust and radio on. There's a softer high pitch whine (like a supercharger) between 30-40mph. It goes away at 40mph, and is then replaced by a lower pitch - but slightly louder - hum between 70-80mph. Sounds a lot like if you're running noisy semi-slick tires on the road. Not sure if heavier diff oil will help reduce some of the sounds but I doubt it. The whine is actually worse at initial deceleration. You might be cruising along with no noise, lift off, and the decel hum appears. There also seems to be a slight bit more driveline vibration felt in the cabin at certain rpms. Feels a bit like an exhaust pipe vibrating against the car chassis.

The good news - No diff whine above 85mph. Above this speed it sounds/feels like before. This is important as 85+mph is my usual cruising speed. Also, while I can definitely hear the whine, for some reason it doesn't bother me. Maybe cos I'm so used to my car being noisy that I just filter it out automatically. Barely 50kms of driving done and the diff whine has already blended into the cacophony of background noise. Or maybe I'm just going deaf.

So, I don't regret getting the powerflex purple diff bushes but you should seriously reconsider if you are concerned about noise.
I have osg lsd too with purple powerflex on 6mt. It's noisy for sure, even running osg's diff fluid.
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      01-11-2020, 02:01 PM   #141
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Quote:
Originally Posted by M43S7RO View Post
Interesting to me that some people get increased diff whine. I went with the purple diff bushings and have a hard time hearing an increase in whine. Almost makes me wish I had just gone for solid, I opted for purple because of reports of whine I had read so wanted to play it safe. Are you manual? Maybe the gear box type makes a difference.

Quote:
Originally Posted by VictorH View Post
Couple of updates. My car of course is back on the road, doing daily driver duties. Regarding the movement some folks feel in the back, I'm not sure you can always attribute that to the rear sub-frame. Low tire pressure, worn-out shocks (probably not very likely, but I felt this in another car), trailing arm bushings that are worn, improper alignment and other factors can all affect rear grip and how the car feels when cornering.

Also, if you look at the design of the rear sub-frame and the front braces, essentially the sub-frame is basically fixed at 6-points. It's hard to imagine you could generate that much movement in the rear sub-frame. I think other factors are more likely.

Regarding the noise issue. Everything is good, the only regret if I have one is the rear differential bushings. I have about 1,000 miles on the set up now and the diff whine has not changed at all, that is it's not any quieter. It's noticeable and I don't really think it's that "cool" unless you just happen to like a noisy car. Having diff whine in back doesn't make a blue-tooth phone call or the stereo experience any better. I'm going to live with it but absent a big power adder, such as a supercharger, I'm not sure adding the diff bushings provide any advantage. I never had a broken diff bolt and my stock bushings looked okay too. Honestly, that is the only regret. I don't want to make it sound like it's really loud, it's not, but it's there, it's unmistakable and I get to hear it each and every time I drive the car.
Previous owner did solid subframe bushings and purple diff and I definitely hear whine, especially around 50 mph. Around 75mph it goes away.
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      01-11-2020, 04:24 PM   #142
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That's odd...I have Powerflex Black diff bushings paired with the DEFIV diff brace, MS solid subframe bushings and can only hear a faint whine if I'm really trying to look for it. My exhaust isn't THAT loud but I do hear the Harrop SC whine more than anything...that could be drowning out the sound perhaps.
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      01-11-2020, 05:22 PM   #143
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Probably. I should get a Harrop to mask my diff whine.
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      01-14-2020, 03:34 PM   #144
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^lol Sounds expensive...good luck with that.
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      01-14-2020, 06:58 PM   #145
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Quote:
Originally Posted by pbonsalb View Post
Probably. I should get a Harrop to mask my diff whine.
Just run an open exhaust, probably quite a bit less expensive (not including excessive noise tickets).
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