1990 535i Heatshield Contacting Driveshaft

[Arjay]

So a few thousand miles ago I started hearing a strange scraping sound intermittently. Today I finally determined it happens when braking with some force, not when braking softly, Also happens when taking a rather spirited right hand turn. So I crawled underneath and saw a rusty band about 4" long around the drive shaft, about 18" up from the universal joint, where it obviously is contacting the heat shield above. I've read the posts pertaining to drive shafts and the thing that confuses me as to what will fix the problem is that there is no vibration of any kind when accelerating, no noises other than the scraping noise when braking.
Is this an early symptom indicating the center bearing needs to be replaced? If so I guess I would want to replace the guibo as well? It has 156k on it at this point.
Thanks in advance for any advice!

Arjay

04 E60
90 E34
89 E30

[shogun]

If you want to do it the proper way, then replace all, engine mounts, center bearing, giubo -if applicable for your car, not all have them-, and the transmission mounts. Then the whole drive system is straight again.
Info here
http://www.bmwe34.net/E34main/Maintenance/Transmission/CenterBearing.htm
http://www.bmwe34.net/E34main/Maintenance/Engine/Mounts.htm

As for the rusty band: is that maybe a wire loom? Because the O2 sensor is located there http://www.bmwe34.net/E34main/Maintenance/Gen_maintenance/O2_sensor.htm

[632 Regal]

I am confused as to the rusting band thing. I would guess this is your center support for the driveshaft. The heat shield above is a type of blanket thing that insulates and falls down over time with oil and trans fluid and can contact the guibo and shaft. The driveshaft is covered on the bottom to protect it from the exhaust heat.

My 530 had a grinding bearing noise and disappeared after a while. This was the actual disintegration of the center support bearing. Everything was quiet for a few thousand miles until the guibo started to fall apart. Once in there I saw the center support completely messed up. No clue how it worked so long.

Just replacing the center support and guibo fixt it all. Might want to replace the pilot guide in the front of the driveshaft while doing the guibo.

[Arjay]

I am confused as to the rusting band thing. I would guess this is your center support for the driveshaft.

Thanks to you both for the quick replies. To clarify what I mean by the 'rusty band', it is just a 4" long area around the circumference of the rotating drive shaft where the coating or paint has been scraped/scratched off to the bare metal by the contact with the heat shield which has just oxidized over time.
Can't figure why just that short length of surface is being scratched or why the noise only happens when braking? Would the shaft be arching in some way due to worn parts ? I can't imagine how there would be any back to front force on the shaft during braking that could cause that?

[632 Regal]

The first heatshield you see is the aluminum one keeping the exhaust heat away from the driveshaft and interior panels. The next one above is a fiber/mat type of thing with an aluminum tinfoil that goes above the transmission and exhaust areas in front. I think this does not go back far enough to be the culprit.

It sounds like your driveshaft must be hitting the bottom shield to wear the paint off. Is there any way to verify anything wrong without taking the exhaust down?

Let me check the web...

Here are a couple pictures:

http://www.bmwe34.net/E34main/Maintenance/Transmission/CenterBearing.htm

I don't know why it would rub while braking but on turns would lead me tho think the center support bearing and or mounts. If the engine and trans mounts are real bad the engine may be moving and pushing the shaft to one side or the other. Center support may also be causing a vibration but you have not indicated that to be the case.

Sounds like you will have to do a closer inspection in regards to the engine and trans mounts, then from that point you will have to either replace all 4 or move on to the driveshaft. While replacing the trans on my sons E36 we found the driveshaft to have a working center bearing and guibo but the driveshaft universals are worn beyond use. This is what you may discover which will change the direction of your project.

My E34 has a vibration that I believe to be either the guibo/center bearing and or universal joints. When I go under this thing I will have a decent shaft ready to replace the one in there along with the center bearing and guibo. This is a messed up project to begin with so I would want to have all parts ready to replace. If the shaft is fine I will sell it on tha bay to recover some costs. But I am not getting any scraping noise like you are.

I will gamble that your motor and trans mounts may be shot.

Prepare for the exhaust flange studs to break if you end up pulling the exhaust. I don't mean they will, just saying prepare for it so your not down forever. 2 of 3 did on my sons which I did not prepare for and it added extra spice to the project. Thinking back I may have been able to use a nut splitter and then remove the nuts instead of busting the studs (mental note taken). Like Shogun posted, replace it all when your in there so you wont have any problems for another 100+k.

[632 Regal]

Instead of editing the post above, your saying it IS hitting the heat shield ABOVE. Check where the shield attaches to the floor above. If it is a mat type thing it could be soft and heavy with oils and sagging or hopefully just become detached somehow. Keep us updated.