Subframe and differential bushings

[81bear]

Originally Posted by pbonsalb

I was questioning whether those who say the whine is not so noticeable or objectionable have stock exhausts or louder aftermarket exhausts that may drown out some of the whine.

I wouldn't say the exhaust drowns out the whine. If anything it may desensitize you a bit to noise but definitely wouldn't drown it out. To be fair though I have a relatively tame after market exhaust so I might not be the best judge.

For those that don't know or are contemplating this decision between performance and NVH the whine really starts between 55-60 mph, below that nothing.

[pbonsalb]

On my turbo E36 M3 with 75D poly diff bushings the whine is terrible at 50-70 but tolerable at 80. As long as you drive through the objectionable range and do not cruise the highway in it, the whine may be liveable. I'll be doing stiffer diff and maybe subframe bushings this year so I am following these bushing threads.

[steven_s]

wowzers... doesn't sound healthy at all...

[squartus]

My car has had the whine since I did the solid rear diff mounts at 25k so the whine is not from a worn diff. The clunking.. mm could be from the drive shaft since its a two piece, had clunk/lashing in first untill I replaced it with a solid shaft. I could turn the OEM driveshaft with my hand and make it clunk.

[pbonsalb]

Right, DS clunks and diff whines. Soft bushings move to reduce clunk and absorb whine. Not sure you have wear but it is possible. How hard are those 68k miles? Mostly track?

[Hujan]

I doubt the whine is due entirety to a bad diff, though I'm sure a bad diff will whine louder than one that's in good condition.

I will let Malek @ MRF Engineering talk more about this, but we recently tested a diff damper on my car, which has solid subframe bushings and delrin differential bushings. My car is a DCT car and, in my experience, the DCT cars tend to whine more than the 6MT cars.

The damper has, to my ear, completely eliminated the clunks and thumps associated with the solid bushings. It has reduced whine under 60 mph by around 20%. However, it has done very little for the whine above 60 mph. At the peak (84 mph) the whine is pretty much as invasive as before.

I think there may still be room to try different damper setups by playing with size and material, but I am starting to fear that the only way to eliminate most of the whine is to go with polyurethane bushings.

[PeruM3]

That whine is definitely louder than mine.

I have Turners' solid diff bushings and it whines between 40-60mph. It's not as bad as your videos. I can live with it. The car didn't whine with OEM mounts.

I do have a lot of cluncking on my 6MT when driving slowly and in traffic. I though my OEM bushings were broken so that's why I installed the solid ones. Cluncking continues, it's a bit worse but at least I know the diff is not going to fall down. BMW dealer says its normal and happens to most 6MT.

[Hujan]

Originally Posted by PeruM3

That whine is definitely louder than mine.

I have Turners' solid diff bushings and it whines between 40-60mph. It's not as bad as your videos. I can live with it. The car didn't whine with OEM mounts.

I do have a lot of cluncking on my 6MT when driving slowly and in traffic. I though my OEM bushings were broken so that's why I installed the solid ones. Cluncking continues, it's a bit worse but at least I know the diff is not going to fall down. BMW dealer says its normal and happens to most 6MT.

DCT whine is significantly louder than 6MT. I've ridden in two DCT cars and one 6MT car and the 6MT car was much quieter than the DCT cars. This was true even though the 6MT car had solid aluminum differential mounts and the two DCT cars were both delrin. (All three had solid aluminum subframe mounts.)

[Lucrecio84]

My car is manual, the whine is there but easily drowned out with the windows down or radio on. Definitely tolerable so I'm glad because the performance you get in exchange is worth it

[pbonsalb]

Why does the longer diff gear in the DCT whines more if it is moving slower? Stays in the noise frequency range?

[Hujan]

Originally Posted by pbonsalb

Why does the longer diff gear in the DCT whines more if it is moving slower? Stays in the noise frequency range?

I have no idea. But that is my experience and it has been borne out by the anecdotal reports on M3Post. People who say they don't notice or don't mind the diff whine invariably have 6MT cars. The people who complain that the whine is obtrusive tend to have DCT cars.

[pbonsalb]

I notice my E36M3 diff whine is not objectionable at 80 mph but is objectionable at 60 mph in 5th gear. So it could be the rpm at which the diff is turning. The 3.25 in the DCT car will turn more slowly at highway speed than the 3.85 in the 6MT car.

[JEllis]

Originally Posted by Lucrecio84

My car is manual, the whine is there but easily drowned out with the windows down or radio on. Definitely tolerable so I'm glad because the performance you get in exchange is worth it

Yeah in the same boat. I go on road trips with the wife in my car and she doesn't notice it.

A worn driveline will certainly make more noise. I imagine as my car ages, the noise/NVH level will increase.

[Lucrecio84]

Originally Posted by JEllis

Yeah in the same boat. I go on road trips with the wife in my car and she doesn't notice it.

A worn driveline will certainly make more noise. I imagine as my car ages, the noise/NVH level will increase.

yup as long as the wife doesn't notice it, I'm in the clear

[M3 Number 86]

I never understand people who do this before the stock one goes.

How hard are you guys pushing your cars? What is everyone talking about more confident? What is the slop that everyone is talking about? This is me on stock bushings.

I'm confused :

[OM VT3]

Originally Posted by M3 Number 86

I never understand people who do this before the stock one goes.

How hard are you guys pushing your cars? What is everyone talking about more confident? What is the slop that everyone is talking about? This is me on stock bushings.

I'm confused :

Im on my 4th diff

[M3 Number 86]

Originally Posted by OM VT3

Im on my 4th diff

are you just drag racing the shit with launch control all the damn time or something?

[Shredicus]

Originally Posted by M3 Number 86

are you just drag racing the shit with launch control all the damn time or something?

Yeah with like 700hp

[pbonsalb]

Maybe go to the old style 210 diff instead of the less durable M variable.

[M3 Number 86]

Originally Posted by Shredicus

Yeah with like 700hp

well no wonder and a stiffer bushing is the answer?

[Hujan]

Originally Posted by DrFerry

Found out today my car has a worn out driveshaft center coupling - which was causing the M-clunk sound (see earlier posting with videos), AND the whine from the rear end is caused by a worn out differential bearing (nose bearing). So, after 68K miles, I'm no gonna' have to lay out some more cash. Next steps, install new oem driveshaft, go back to soft oem diff bushings, install new diff from diffsonline.com with a Quaife LSD and 3:45 gear. Once done, I'll report back.

http://www.hardemanmotorsport.nl/eng...1_E92_E93.html

Please report back. I'm especially interested in hearing your thoughts on the 3.45. I've long felt that the factory 3.15 is too tall have considered doing a 3.45 myself. (3.62 seems a bit too aggressive for me.)

[whats77inaname]

Originally Posted by M3 Number 86

I never understand people who do this before the stock one goes.

What is everyone talking about more confident? What is the slop that everyone is talking about?

I'm confused :

Drive one that has been upgraded for comparison, and I assure you, you won't have these questions.