E9X Diff Bushing Recommendations

[I am Jacks N54]

Currently looking to install diff bushings on my e90 that sees track duty 2-4 times a year but also shuttles around the kids. Rear subframe has M3 bushings. Narrowed down to a few options but looking for anything I may have missed before making a final decision.

Whiteline KDT911: https://www.whiteline.com.au/product_detail4.php?part_number=KDT911
AKG Poly 95A: https://www.akgmotorsport.com/produ...t-for-bmw-e8x-and-e9x-non-m-polyurethane-95a/

If anyone's got any other offerings to compare, please share. TIA

 

[Torgus]

Hello jack's n54,

Here are some other options on the market for diff bushings: https://www.turnermotorsport.com/BMW-E90-Parts/c-652-bmw-differential-bushings & AKG also makes a 75D https://www.akgmotorsport.com/produ...t-for-bmw-e8x-and-e9x-non-m-polyurethane-75d/ & https://www.condorspeedshop.com/products/e90-combo

I have these solid ones from turner: https://www.turnermotorsport.com/p-...ts-solid-aluminumdelrin-race-e82-e9x-f22-f3x/ with a diff lockdown brace.

You gain Noise, but no Vibration or Harshness in my experience. I have a fair amount of diff whine from my pumpkin with the quaife diff. More than anyone would want in a DD in my opinion. You only hear it on the highway fwiw, you need to be at speed, around town the differential is quiet. Now the amount of gear whine you will get varies from diff to diff I have been told based on how you set the backlash and the design of the differential. I use fancy fluid, made no change in sound.


I would argue if you switched to solid subframe bushings, instead of the m3, there would be no added NVH. Might be something to consider in the future.

 

[ShocknAwe]

Do solid subframe and stock differential. Reverse is noisy as hell.

 

[I am Jacks N54]

Good info, thanks guys. I considered aluminum diff bushings briefly until finding this:

I'm too old for that shit.

The subframe bushings are still in good shape, but I'll likely go the solid route once they start to fade. I'll probably go with the AKG's for diff. I've had good luck with their products.

 

[Asbjorn]

Good info, thanks guys. I considered aluminum diff bushings briefly until finding this:

. I'm too old for that shit.

The subframe bushings are still in good shape, but I'll likely go that route once they start to fade. I'll probably go with the AKG's for diff. I've had good luck with their products.

I run solid sub-frame mounts in combination with powerflex purple (road series) differential bushings. No audible differential whine with this combination. And I have a quaife core installed. If you get whine with this setup it is because your differential is dying. I know this first hand...

I haven't tried the black series / 95A type differential poly mounts.

EDIT: oh and almost forgot: I highly recommend solid sub-frame mounts. Feels great to drive.

 

[fmorelli]

You gain Noise, but no Vibration or Harshness in my experience. I have a fair amount of diff whine from my pumpkin with the quaife diff. More than anyone would want in a DD in my opinion. You only hear it on the highway fwiw, you need to be at speed, around town the differential is quiet. Now the amount of gear whine you will get varies from diff to diff I have been told based on how you set the backlash and the design of the differential. I use fancy fluid, made no change in sound.

I run solid sub-frame mounts in combination with powerflex purple (road series) differential bushings. No audible differential whine with this combination. And I have a quaife core installed. If you get whine with this setup it is because your differential is dying. I know this first hand..

@Asbjorn can you say a sentence or two more on "dying"? I maybe incorrectly recall you thought there was an issue with installation, the first time around, and you had it redone? I only mention this given @Torgus comment. This may not be a Quaife issue as much as how it is set up.

Dan @ Diffsonline is the guy to talk to on BMW diffs, if in the USA.

Filippo

 

[Torgus]

I think he is saying with softer poly mounts if you have diff whine it is because of your differential is starting to fail. I have solid diff mounts and a lock down kit. I have whine but it is not as bad as that 350Z video.

I notice the diff whine above 50 mph IIRC. But I also have the turbo whine from the T51R mod, BOV going psssh psssh. Car makes lots of noises almost constantly now.

Any upgrade is better than the stock or m3 diff bushings. I'm sure the poly give close to the performance of the aluminum but without the added whine.

 

[ShocknAwe]

I think he is saying with softer poly mounts if you have diff whine it is because of your differential is starting to fail.

I have solid diff mounts and a lock down kit. I have whine but it is not as bad as that Z video.

I have a lockdown, stock mounts, clutch diff and zero whine. I had a shit ton of whine with my stock diff at 80k miles, and mild whine with my mfactory diff throughout it's whole life.

 

[Asbjorn]

@Asbjorn can you say a sentence or two more on "dying"? I maybe incorrectly recall you thought there was an issue with installation, the first time around, and you had it redone? I only mention this given @Torgus comment. This may not be a Quaife issue as much as how it is set up.

Dan @ Diffsonline is the guy to talk to on BMW diffs, if in the USA.

Filippo

Here's want happened with my diff setup:

I did the poly bushings together with the first quaife installation on my car. Then I got diff whine. Back then I assumed it was due to the poly bushings. After several thousands miles, the diff broke (the whine got exponentially louder). Then I installed a new diff, while keeping the same bushings, and the diff whine was gone. Then I reinstalled the quaife core in the new diff and installed solid sub-frame mounts. Still no whine. Diff has been fine for thousands of miles now.

We believe the reason the first diff broke was due to an error during the quaife core installation. But we do not know for sure if it was wrong backlash setting or something else that caused it. Anyway, it was definitely not a quaife product issue. The quaife core lives fine and well in the new diff I use now. The second time I had it installed I used a more experienced shop, and they did a better job. We re-checked backlash on the new diff not long ago, and it is still fine, and there's no metal in the oil or other indicators of it failing again.

 

[Asbjorn]

I think he is saying with softer poly mounts if you have diff whine it is because of your differential is starting to fail.

I have solid diff mounts and a lock down kit. I have whine but it is not as bad as that Z video.

Yes exactly