Rear diff. bushings AKG vs RE vs Revshift vs Condor

[dukeofchen]

Nothing to add but interesting discussion, in that there are so many variations of poly and some do sound truly terrible anecdotally, whereas others seem like a more reasonable compromise against the current crowd consensus of OE.

I'm due for a refresh and was only looking OE, but I'm also lazy so one-and-done has a certain appeal, and if there's a cost / benefit to NVH vs. feel I'd certainly give it a second thought. That and the fact that every car has varying degrees of wear or upgrades throughout the drivetrain, so it's not as if a review of a single bushing is absent confounding factors.

Feels like the shades of grey are less often discussed these days (universally).

[SQ13]

I installed my AKG 95A diff bushings in Jan 2015, and the whine has gotten louder over the years. I’ll be switching back to OE diff bushings this summer.

[TheElite///M3]

I'm currently switching out the Condor white poly mounts full set (motor/tran/diff) for RevShift green (i think are 85A duro). I got the motor mounts in, then moved the car and it definitely improved the NVH. I'll be changing the diff too from rebuilt and will report my findings once this Cali rain subsides. I'm building for Canyon occasional HPDE.

On my RS7, i'm upgrading the mounts to 034 Motorsports cavity filled which they also make an OE e46 m3 mount as well, if you're looking for OEM+ comfort.

[old///MFanatic]

I'm currently switching out the Condor white poly mounts full set (motor/tran/diff) for RevShift green.

You sure your differential mounts from Condor are white poly? From what I recall their Condor diff bushings are like a hard solid Delrin material. And since this thread is only about diff bushings that’s an important bit of info to clarify.

[TheElite///M3]

You sure your differential mounts from Condor are white poly? From what I recall their Condor diff bushings are like a hard solid Delrin material. And since this thread is only about diff bushings that’s an important bit of info to clarify.

I’m not sure until they come out, which I’m happy to confirm. I’m between cleaning my diff cover with my wife’s toothbrush and a f8x driveshaft conversion.

For Condor engine and tranny mounts, I presumed to think why not the differential in the same material. I thought I may have been misinformed however on further investigation, to find that the Condor site lists as polyethylene (attached below). I looked up the differences in UHMW, Delrin and Polyethylene, and believe my assumptions as true. Again will confirm when it’s physically in my hands and will maybe do a comparison. Thanks again for helping me to clarify. Love this forum.

[old///MFanatic]

For Condor engine and tranny mounts, I presumed to think why not the differential in the same material. I thought I may have been misinformed however on further investigation, to find that the Condor site lists as polyethylene. I looked up the differences in UHMW, Delrin and Polyethylene, and believe my assumptions as true. Again will confirm when it’s physically in my hands and will maybe do a comparison. Thanks again for helping me to clarify. Love this forum.

Yeah didn’t think Condor made polyurethane diff bushings. It’s very solid plastic. I have their subframe bushings. Better than aluminum in some regards but basically just as solid in its performance. So if you have solid bushings that’s a big compromise.

[old///MFanatic]

Also, the main "downgrade" is noise (whine) which I almost complete eradicated with some lightweight sound deadening foam under the rear bench.

Again, could you share which exact brand and type of material (or durometer) you used? Since you had such good results.

[Tbonem3]

AKG black (90 or 95a, can't remember). Diff and sub. One is 90 and one is 95, both black aka "street"

Something else worth mentioning while discussing NVH - final torque value.

An over tightened bolt/nut could transmit more unwanted NVH, irrespective of bushing material.

[dukeofchen]

Thinking out loud but aren't interactions between NVH coming from the differential, subframe and RTABs a consideration here?

Given most people on here are moving to solid subframe bushings, wouldn't those increase transmittance of NVH from stiffer diff bushings, as opposed to stock rubber or a softer poly?

In which case OE / solid at diff / sub is a combo people like, poly / solid increases NVH, and poly / poly is somewhere in between depending on duro?

[Tbonem3]

Much NVH doesn't seem to be transmitted by the subframe, no matter what bushing material. I think the idea is that the rear suspension (rubber isolators, damper, spring, tire, bushings) should absorb all the enegry before it gets to the subframe, then body panel.

With the diff, I think it's that there is so much more NVH due to the nature of the beast (extreme pressure gears turning high velocity) that you will have to deal with some NVH, and the stock foam, despite its thin cushion, eats up that NVH very well.

So, as we see in real life, solid subframe bush = no increase in nvh. Any harder material than stock in diff = substantial NVH increase.

[Projecte46m3]

AKG diff bushings ane CMP subframe bushings 👍

[old///MFanatic]

AKG black (90 or 95a)…

Interesting is that even AKG lists those as “Performance/Track” and NVH: Medium

[Nate047]

I have poly in my car, they came with the car so I am used to it. I've also driven a freshly restored original car, and a couple of other original-ish cars of various wear stages.

It's all about perspective. Is your car stock and do you like things to be quiet? Or do you like some because racecar sounds?

Want to quote myself and eat some crow here. After getting my car put back together, the noise is WAY worse. I changed the front diff mount from ECS poly to PowerFlex poly, which I think is harder. I also went with solid subframe mounts. Also, I removed a bunch of sound deadening and rear interior. So I guess just consider ALL factors of your specific build before jumping in. I’m going to run this for a while and see if I can get used to it. But basically it’s all the clunk and no “cool” sounds. It sounds like something is loose or broken in the rear end. It’s louder than my exhaust too which is a fun side note.

[Slideways]

Want to quote myself and eat some crow here. After getting my car put back together, the noise is WAY worse. I changed the front diff mount from ECS poly to PowerFlex poly, which I think is harder. I also went with solid subframe mounts. Also, I removed a bunch of sound deadening and rear interior. So I guess just consider ALL factors of your specific build before jumping in. I’m going to run this for a while and see if I can get used to it. But basically it’s all the clunk and no “cool” sounds. It sounds like something is loose or broken in the rear end. It’s louder than my exhaust too which is a fun side note.

Having the full rear interior in will dampen a lot of diff and rear suspension noise.

Driving with the full rear interior removed and stock everything, you get some very tolerable diff whine which does make the car sound more race car in a cool way (only for a short stint). To get an idea of what diff noise is like for anyone considering solid anything, just remove the rear bench and seat backs.

Driving with the full rear interior removed and all new stock bushing with the only change being solid subframe bushings, the diff noise is no longer tolerable, especially under acceleration. Diff whine is very irritating, just as much as exhaust drone, imo. They both tend to be constant noises. After putting back the full rear interior, the diff noise is 95-99% muffled by the rear bench and seat back and the noises in the cabin become very tolerable.

[Nate047]

Having the full rear interior in will dampen a lot of diff and rear suspension noise.

Driving with the full rear interior removed and stock everything, you get some very tolerable diff whine which does make the car sound more race car in a cool way (only for a short stint). To get an idea of what diff noise is like for anyone considering solid anything, just remove the rear bench and seat backs.

Driving with the full rear interior removed and all new stock bushing with the only change being solid subframe bushings, the diff noise is no longer tolerable, especially under acceleration. Diff whine is very irritating, just as much as exhaust drone, imo. They both tend to be constant noises. After putting back the full rear interior, the diff noise is 95-99% muffled by the rear bench and seat back and the noises in the cabin become very tolerable.

I’m uploading a video right now, it’s low speed just around my neighborhood so it’s not so much the diff whine, but the clunking which is much more immediately noticeable.