Aluminum diff bushing sound question

[Mackshackm3]

Well my original/oem diff bushing/s finally crapped out on me the other day.

Love the sound of solid aluminum bushings on a couple of YouTube videos I’ve seen. Reminds me of the whine straight cut transmission gears on race cars have.

Wanted to get some feedback from members that had installed them and see how they like them.

1) is the sounds mostly under acceleration/engine brake? Or is it just as loud coasting at constant 65mph on flat highway?

2) is the sound bearable or obnoxiously loud/drone like?

3). Can you hear the whine on city driving or is it mostly at fast highway speeds?

All the m3 solid diff videos I’ve found have been short , highway speed pulls….trying to gauge what the overall driving experience is with these.

My car is not a daily driver and gets the exact same use a sports bike. Saturday/Sunday spirited driving with rare and ocasional track days.

[PSUEng]

So I'm way out in left field here with my response but take it for what it's worth. My car is on [new] stock diff bushings and trans mounts so I have no experience and cannot directly answer your question with E46 M3. But, I had a '21 STI totally stock--put a poly front shifter bushing thinking I liked that straight cut gear whine sound of the older STIs...well, turns out, by the end of it all before selling it, I had gone from loving it to hating it all because of the sound/whine--it shifted great however. But in the end, it didn't really really sound like straight cut gear whine, but rather, just introduced a bunch of NVH at idle, whine at certain RPM, and just wasn't that great. AND my wife damn near refused to ride in the car. Anyway--for me, I'd chase that sound too, but you may end up with something you don't want over time. And diff bushings aren't such and easy swap on these cars, at least in my world.

[Mackshackm3]

So I'm way out in left field here with my response but take it for what it's worth. My car is on [new] stock diff bushings and trans mounts so I have no experience and cannot directly answer your question with E46 M3. But, I had a '21 STI totally stock--put a poly front shifter bushing thinking I liked that straight cut gear whine sound of the older STIs...well, turns out, by the end of it all before selling it, I had gone from loving it to hating it all because of the sound/whine--it shifted great however. But in the end, it didn't really really sound like straight cut gear whine, but rather, just introduced a bunch of NVH at idle, whine at certain RPM, and just wasn't that great. AND my wife damn near refused to ride in the car. Anyway--for me, I'd chase that sound too, but you may end up with something you don't want over time. And diff bushings aren't such and easy swap on these cars, at least in my world.

thats is great feedback! Really appreciate you sharing your experience. Exactly my concern…..the videos I’ve seen sound great on a highway acceleration pull but how do they sound during normal driving…..

I may end up going with it since I’m doing the work myself and I’m planing on doing the subframe reinforcement when the weather cools down. Worse comes to worse I’ll have the annoying sound for 6 months and I’ll be out $150 but can revert back to stock when the subframe is out.

[bigjae46]

Diff whine is THE most annoying noise and its loudest right between 70-80mph. It makes me think of a dentist drill. I solved the noise by installing a BW race exhaust and headers...fight noise with more noise.

[9kracing]

it's louder than you think

https://youtu.be/qquD1i5V0cY?si=sD-ngQRiKDXK7B16

[Arith2]

I have solid subframe bushings with poly diff bushings. It's already loud. My exhaust covers up the sound mostly but it still resonates through the body in a way microphones won't pick up. I'm ok with poly bushings as my engine mounts and trans mounts are also poly but you'll hear sounds that will disturb you. It's a different chassis so all the sounds will be different on how they resonate from the STI. My SMG shifts so much better though. It's stupid fast and I can hear all the bits moving around so it sounds pretty sweet.

At about 90 is when drive train noise starts to get loud for me so I can imagine it'd be obnoxious at 50 for solid mounts. It will make noise under acceleration but cruising will still be bad. Rolling the windows down will become a norm so you aren't trapped in a sound box. Race cars have a race team and spare diffs to throw in, backed by sponsors with money. You will accelerate wear on your diff or expound on an existing problem.

[EthanolTurbo]

Poly diff bushings suck ass and make a ton of annoying NVH. Highly recommend only using stock.

[simonnim]

I am running poly on subframe and diff. It does ass noise, and emphasizes the e46 shifting clunk. If it's a daily I'd probably go stock/OEM. As a weekend car it's fine with me.

[Arith2]

I don't mind poly bushings at all. If you're sensitive, stay OEM. Most are sensitive which is fine.

[Casa de Mesa]

I have solid diff bushings. Worst "upgrade" I have ever done. Diff whine isn't a great sound and doesn't sound (much) like straight cut gears.

When I work up the energy to swap back to stock, I will. Solid suspension bushings/monoballs I can hack all day long, but solid diff bushings, I had no clue how much I'd hate it.

I suppose everyone's tolerance for different noise frequencies probably differs a great deal, but it seems the vast majority of people on this forum almost universally agree "avoid it at all costs".

[heinzboehmer]

I have solid diff bushings. Worst "upgrade" I have ever done. Diff whine isn't a great sound and doesn't sound (much) like straight cut gears.

When I work up the energy to swap back to stock, I will. Solid suspension bushings/monoballs I can hack all day long, but solid diff bushings, I had no clue how much I'd hate it.

I suppose everyone's tolerance for different noise frequencies probably differs a great deal, but it seems the vast majority of people on this forum almost universally agree "avoid it at all costs".

Saaaame (except I have poly). But I agree with everything you said.

[Fresh6390]

Seems consensus is to buy new rear diff cover for the bushings. What about the front diff bushing that mounts diff to subframe? Is poly okay here or is oem rubber the recommended?

[Tbonem3]

OE is foam, not rubber, and they're quite stout, but still factory level of isolation.

I like the middle ground of black poly. Not too much whine, but crisper accel. I put some light foam under the rear bench and basically eliminated any whine. I doubt that'd help enough, with solid delrin/alloy.

I drove a solid bushed rear end e46 m3 and didn't like it after about 20 seconds. Watch you tube vids to get your straight cut fix imo.

[Stilt]

Solid subframe bushings, oem front diff bolt bushing, & for the rear diff cover use oem e36 m3 bushings 🤌


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[Fresh6390]

OE is foam, not rubber, and they're quite stout, but still factory level of isolation.

I like the middle ground of black poly. Not too much whine, but crisper accel. I put some light foam under the rear bench and basically eliminated any whine. I doubt that'd help enough, with solid delrin/alloy.

I drove a solid bushed rear end e46 m3 and didn't like it after about 20 seconds. Watch you tube vids to get your straight cut fix imo.

Thanks for input. I already have condor front diff bushing in garage but starting to second guess in terms of nvh.

think I my guess run it though.

subframe - condor
diff - oe
Front diff- condor
Rtabs - condor

Hope doesn't bite me later.