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      11-22-2019, 01:06 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, 05:29 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, 05:40 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, 07:00 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, 10:58 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, 12:05 AM   #138
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I thought it's always the front ones that break?
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      01-11-2020, 01:52 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 09:27 AM..
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      01-11-2020, 09:14 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, 01:01 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, 03:24 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, 04:22 PM   #143
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Probably. I should get a Harrop to mask my diff whine.
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      01-14-2020, 02:34 PM   #144
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^lol Sounds expensive...good luck with that.
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      01-14-2020, 05:58 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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      03-01-2020, 09:33 AM   #146
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I just replaced the rear subframe and diff bushings and thought it might be worth sharing my experience. This thread seemed like a good place to make a post. I installed AKG 75D subframe bushings and PowerFlex purple diff bushings. I read this work (with split poly bushings) could be done without complete removal from the car. I gave it a try and it worked out. Replacing the engine mounts has a sort of similar process for lowering the front subframe. Photos added at the end of the post.

Getting the diff out was easy, and to that point my work was basically a duplicate of Victors. I was able to replace the diff bushings with the subframe in the car.

I bought the eBay subframe bushing tool that Victor used for removal and ended up stripping the threads of both shouldered nuts and the threaded rod while working on the front bushings. Either my electric impact broke the tool, or I did something to break it. I have other press tools that I could scavenge from and made something work but could only use hand tools. The rear bushings could be removed from the bottom, but not the fronts. For the fronts, I needed enough room between the body and subframe to pull from the top. The bushings have a rubber coated metal shoulder that wouldn’t come out the bottom with the tools I have. Like Victor said the shoulder seems to break on purpose and that’s a good thing. Disconnecting the hydraulic brake lines is still mandatory.

As far as subframe alignment, I marked points on the subframe and body. The AKG bushings have a very tight fit on the front alignment dowel. I could not move the subframe around once the dowels were in the bushings. Fortunately, all my marks were aligned, and no further adjustment appeared needed.

Torque specs from TIS that matter:
Front and Rear Diff Bolts – 100 Nm
Lower shock bolt – 100 Nm
Axel Bolts – 120 Nm
Driveshaft – 20 Nm + 90 degrees
Subframe Bolts – 108 Nm
X-pipe Bracket – 24 Nm
Tension Strut Rear Bolts - 47 Nm + 90 degrees

Here is what seemed notable to me:
1. Hydraulic brake lines: In addition to the brake/clutch pedal hold tool I used these line plugs: https://www.belmetric.com/advanced_s...rake+line+plug
2. Lowering the subframe: I used a floor jack at the rear of the subframe and a harbor freight transmission jack at the front, with rubber jack blocks between each jack and the subframe. To be honest, it was a little wobbly when I was doing the work, but I did not feel unsafe since I was not under the car and it never felt like it was going to tip over. If I were going to use a different lifting tool I would use a motorcycle jack and build a wood platform (similar to what Victor used), which I will likely buy anyway since it looks like it will work well for other things. The process is to lower it a little at each end until there is enough room to pull the bushings.
2. There are two bolts holding the parking brake cables to the body in the drivetrain tunnel above the driveshaft. I removed those to permit some additional clearance and flexibility. The parking brake cables can flex a good amount. This may not be necessary, but I did it while I was trouble shooting early in the process and it looked like an issue then. If someone does this, then do it before you remove the diff, and reinstall after the diff is in place and bolts are torqued to spec. There is more room to R/R the front diff bolts this way.
3. The electric wires in the back of the rear wheel wells need released from their plastic clips on the subframe, same as Victor did. I did not remove the wheel well liners, nor did I undo the electric connectors.
4. Removing the rear tension strut bracing was mostly similar, but not different enough to really need a description; it depends on how someone would support the driveshaft and x-pipe. Two of these bolts are the front subframe bolts. I did one side at a time and threaded the bolts back in when one tension strut was removed.
5. Driveshaft: TIS says the driveshaft is balanced, that there are marks on diff input flange and there is a corresponding bolt with a washer. I had the marks on the diff flange and a bolt had a washer, but they were not aligned like TIS says…..I am guessing a previous owner had work done in the area. In any case, I marked things before disassembly and just put things back together in the same spots since I did not have any vibrations previously.
6. Axel bolts: Releasing the parking brake cable from the hooks on the subframe can provide a little more access to axel bolts, but you will still have to put your car in neutral and rotate the axels to get the specified torque on each of the bolts. For manuals this means parking brake off and out of gear. I have a DCT and it was easiest for me to turn the car on for a few seconds, put it neutral with parking brake off and rotate an axel by hand. I figured people here know that but reading some threads on this website it’s clearly not common knowledge. “Good and tight” and “TAF torque spec” doesn't work for me. Same deal with the driveshaft.

The difficulty of this project does not match its reputation. It’s big and heavy parts, but it’s not complicated. If someone has a way to lift and hold with multiple tools that is half of what there is to figure out. The other half is having a way to R/R the bushings. This ended up being a much longer post than I wanted to write, and I did not write everything out. Most of what Victor posted applies to just lowering the subframe, so, there was no need to rewrite everything. The online version of TIS has all the information and there is no need to duplicate that either.

Rear Diff bushing


Front Diff Bushing


Rear Subframe


Front Subframe


Subframe gap

Last edited by chalbe; 03-08-2020 at 03:45 PM.. Reason: added torque spec for tension strut bolts
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      03-01-2020, 11:05 AM   #147
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Great work! Driving impressions?
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      03-01-2020, 12:33 PM   #148
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None yet. I don't think driving around my neighborhood counts, but in those cases the car feels normal. I will know more in a few weeks when it gets warmer, and after the first couple of local-ish autox test and tunes.
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      03-01-2020, 08:23 PM   #149
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Been wondering if aftermarket mounts inadvertently change the sub-frame position in relation to unibody. Even the single piece have a raised section where it attaches to the unibody suggesting the mount height is the same although I never measured before and after

This would slightly impact anti-squat geometry.
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      03-16-2020, 11:52 PM   #150
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broke a differential bolt sliding around not too long ago biggest disappointment so far... definitely upgrading my diff bushings to purple dont care if it whines a little its a weak point that needs it. i push this car sometimes i cant have it breaking on me like that. not worried about our sub frame though.
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      03-17-2020, 07:25 AM   #151
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It does not happen to many but it has happened to a few. I run stiffer diff bushings for exactly that reason and put up with a little whine. Mine are AKG black, so 95A. Powerflex purple are 80A, much softer but still slightly harder than rubber.

Which bolt broke? One of the fronts or the rear?
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      03-17-2020, 09:33 AM   #152
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Quote:
Originally Posted by pbonsalb View Post
It does not happen to many but it has happened to a few. I run stiffer diff bushings for exactly that reason and put up with a little whine. Mine are AKG black, so 95A. Powerflex purple are 80A, much softer but still slightly harder than rubber.

Which bolt broke? One of the fronts or the rear?
I wonder if purple is noticeably less whine than black or not?
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      03-17-2020, 10:55 AM   #153
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Anecdotal reports are that purple still whines. Makes sense it would be less than black, which would be less than red or delrin or aluminum.
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      03-17-2020, 05:27 PM   #154
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Still thinking about 80a or 95a poly to replace the OE foam mount, but OE rubber in the other 2 spots. I would replace bolts when swapping mounts.
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