help identify noises in S50E30

[static]

Hi all, a bit long but please bear with me

After i did the S50 conversion the extra noise had been driving me insane. Please help me identify what it can be

Here are the description and symptoms:
Noise is of humming / buzzing / grunting / whining / vibrating type and fills up the cab as soon as windows are rolled up, making me feel like i am in acoustic torture chamber.
Noise is most prominent when the car is under load, it feels like the noise produced by the engine (normally isolated from body with help of engine mounts) gets into the cab through "loaded" driveline components (only when they are being under load). Noise gets more prominent on highway, i guess due to increased load on the driveline.
If i go to neutral and rev engine the noise is not there, so it's definitely load related.

I also get metal scraping/dragging noise when on highway doing 90-100mph and lift the accel completely. Even if i push accel ever so slightly, the scraping noise goes away.

Here are the parts that i used/changed:
- E28M5 cylindrical rubber motor mounts (with 5mm spacer on the driver side)
- UUC red tranny mounts with enforcers (torqued per spec)
- new stock guibo and center bearing
- IE urethane (street) subframe and trail arm bushings
- new fluids in tranny, diff

old related parts, not changed:
- old halfshafts (boots in good condition)
- E36M3 used driveshaft (not taken apart so is still balanced)
- old wheel bearings
- used diff with unknown history, but seals and fluid are changed.

other:
- the trunk insulation had been taken out (perhaps exacebrating the noises)
- exhaust is a bit loud, but as i mentioned noise goes completely away when revved freely (not under load), so shouldn't be the culprit

Thanks a lot
Alex

[PiercedE30]

wheel bearings and your diff.
The sound from when your drivetrain is under load is the sound from the diff being transmitted, and added to by the wheels bearings, through your subframe and trailing arm bushings. I have the same problem, but minus the s50.
Change your wheels bearings and put some thicker, or just an additive, oil in your diff and see how it sounds.

[static]

Thanks for reply

I can understand the diff transmitting noises to subframe and body, still strange tho, since driveline isolated from engine by the rubber guibo.

Why do you think wheel bearings add to the problem? As i mentioned, if i cruise on highway if i clutch in the noises are gone. I'd think that wheel bearing noises depend on speed and would stay no matter what i do with clutch, no?

Anyone else would like to offer their educated guesses?

[Mike B.]

Is it just noise or is there noticeable vibration as well?

[static]

actually i've driven it with earplugs for couple of days (this is the extent of annoying noise giving me headaches) and felt quite a bit of vibration (i guess it's easier to feel the vibration without hearing the noise). It also could be that the noise results from vibrations transmitted to the body.

[Mike B.]

It's hard to trouble shoot without hearing/feeling what you are describing. That being said, I have a few questions...

Did the driveshaft spin freely in the CSB before you installed it? Did you preload the CSB? Did the transmission/driveshaft come out of a wreck? Guibo properly torqued?

Any driveline vibrations are going to be sent right into the cabin because of the re-inforced transmission mounts and poly bushings.

[static]

parts from a wreck? not sure, shaft looked to be straight and undamaged.

swap was performed by a very good mechanic, who performs these jobs (shaft, guibo, bearing...) on daily basis. He specializes only in bimmers.

i could probably record a video, but most of the sounds are very low pitch and perhaps won't be picked up by camera adequately.

[Mike B.]

I the reason I ask about the wreck, is that everything else seems to be installed correctly.

You might want to check run-out or for play on the output shaft on the trans, u-joints on the driveshaft and input shaft on the diff. If it is even slightly off, the whole thing will vibrate under load (shaft turning).

Have you mentioned this to the mechanic that did the install?

[static]

yes i mentioned, and i have yet to go with him for a ride to let him hear the sounds. Just decided to ask you guys beforehand.

[static]

so i've taken the rear seat out in preparations for b-quiet'ing the car. Driven for a while and now i am 100% sure that all these nasty sounds are coming from the rear. Taking seats out made the sounds like 3x louder.

Again, it's humming/droney kind of noise only whe the engine is connected to the wheels (i e. accelerating or coasting in gear). When i completely let out throttle on highway, it gets really loud.

could that still be rear bearings? or not, since sound seem to disappear once i clutch in.

Thanks
Alex

[aaron.j]

you have urethane parts on your vehicle. live with it.

[static]

you have urethane parts on your vehicle. live with it.

i would, only if i new for sure that there is nothing else is wrong with the car, and that those sounds are perfectly normal for an e30 with same setup as mine.

[aeryk7]

Check to see if your exhaust piping is touching your cross member or control arm bushing. Also check brake booster manifold clearance.

[static]

Check to see if your exhaust piping is touching your cross member or control arm bushing. Also check brake booster manifold clearance.

got under the car yesterday and checked every inch of the exhaust for touching anything, even pounded on it to see if it moves to much - it's not the exhaust.

booster, OTOH, is like 1mm away from the manifold. I noticed this problem before and stuck a rubber gasket between those two - made no difference in sound really.
Have you heard of anyone experiencing loud noises due to those two touching?

[aeryk7]

I was gonna say disregard my previous post but i experienced those symptoms with my car.