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7 Series - E38 (1995 - 2001)

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  #1  
Old 07-11-2013, 04:19 PM
edognight edognight is offline
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Location: St. Paul, MN
 
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Mein Auto: 1997 e38. schwartzx2
Horrible Horrible noise from the back right.

Now that my car is running, new problems!

It has the loudest thumping and grinding, from a stop to about ten miles an hour, in the back right, I swear I was gonna look under there and find the axle shafts bent to 90 degrees, but I looked under there, and it LOOKS perfect.

It is related to the drive shaft speed, it builds, gets louder, and louder, and grinds and thumps horribly, then goes away and the car glides along perfectly.

When it is loud, it thumps, and I swear you can feel it hitting the inside of the fender well.

Axle shaft? Drive shaft? it's really, really bad.
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  #2  
Old 07-11-2013, 08:16 PM
ebida3's Avatar
ebida3 ebida3 is online now
Society of the 7's East
Location: High Point, NC
 
Join Date: May 2010
Posts: 548
Mein Auto: 2001 740iL
Possible reasons for noises in the rear....

1. CV joints
Look for the classic tell tale ripped/torn boot. As dirt gets in there it grinds the joint. A bad joint usually will make noise on a turn. The turn stresses the joint and causes the joint to click, snap or grind.
2. Wheel bearings
Same as above without the boot. Same diagnoses process
3. Universal joints
Use a pry bar and look for any play, there should be none. Bad U-joints will thump and then go quiet at higher speeds. Bad joints also cause the Guilbo disc to go bad. (See below # 8)
4. Inner fender well
Make sure the inner fender well isn't rubbing against the wheel.
5. Exhaust system
Look for the pipes hitting the drive-shaft. Also look for broken exhaust mounts and hangers.
6. Rear carrier bearing(s)
Bad carrier bearing(s) tend to whine and whirr depending on the severity they too can quiet at higher speeds.
7. Fuel tank
The tank may implode due to vacuum being created. The fuel cap doesn't vent correctly. Leave the fuel cap off and see if it stops.
8. Center flex disc or Guilbo disc The center support for the shaft develops too much play and knocks like mad. When coasting it does not make any noises only when accelerating at the low rev range. Same procedure as checking u-joints
9. Center prop-shaft floor bracket These crack and lose their support causing a thumping too. Visually look at the bracket

Whew! I believe I got most of it.

You may want to do a differential service.
There is a kit that includes
* Three bottle of Genuine BMW Limited Slip Gear Lube
* Two New Genuine BMW Drain/Fill plugs
* Drain plug O-ring

Pick one
Good Luck

Last edited by ebida3; 07-11-2013 at 08:45 PM.
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  #3  
Old 07-12-2013, 05:37 AM
edognight edognight is offline
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Mein Auto: 1997 e38. schwartzx2
Thanks

I will do when I get some time this afternoon. Reading your list, the center flex disc is very suspect. The thing made so much noise, I cant believe I can't see it. I thought there would be a train wreck down there.

Im goin in with a pry bar, and some jack stands and see whats up.
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  #4  
Old 07-12-2013, 08:05 AM
JasonSC540ia JasonSC540ia is offline
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+1 for wheel bearing. Grinding sound associated with speed, 95% its going to be a wheel bearing. Get the rear tires up in the air, nutral with no parking brake and spin. You should be able to pinpiont it. If one side is bad the other is probably not too far behind, so I would suggest changing both.

Good luck on locating your problem, and please reply back and let us know what you found.
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  #5  
Old 07-12-2013, 06:50 PM
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ebida3 ebida3 is online now
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Jason a bad bearing will whine louder as u sway to shift weigh on it. If you sway back and forth you can hear the bearing whine louder and lower. A constant knock regardless of sway may not be a bearing.
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  #6  
Old 07-13-2013, 07:38 AM
edognight edognight is offline
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It has to be in the drive shaft. The axles are tighter than a drum, I cant get them to move at all. Gonna drop exhaust, heat shields and see...
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  #7  
Old 07-15-2013, 03:19 PM
edognight edognight is offline
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Mein Auto: 1997 e38. schwartzx2
CSB Gone

The Center support bearing is totally gone. Just the metal hoop. It would clank like hell on the trans tunnel and quit about 15 mph. You can see the little dings where the drive shaft was hitting the tunnel, and it is a little marked up, but not horrible.

Rubber flex disc and rear CV joint look perfect, and I can get zero play out of them with a crowbar.

So off to the online parts bin place, and stuff.

Lots of work, but hopefully not too much money. Thanks for the help, guys.
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  #8  
Old 07-15-2013, 07:30 PM
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ebida3 ebida3 is online now
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Location: High Point, NC
 
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Talking

So nice when a plan comes together!!
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  #9  
Old 07-16-2013, 08:25 AM
JasonSC540ia JasonSC540ia is offline
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Quote:
Originally Posted by ebida3 View Post
Jason a bad bearing will whine louder as u sway to shift weigh on it. If you sway back and forth you can hear the bearing whine louder and lower. A constant knock regardless of sway may not be a bearing.
Good call. Sounds like he nailed it.
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  #10  
Old 07-16-2013, 04:19 PM
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ebida3 ebida3 is online now
Society of the 7's East
Location: High Point, NC
 
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Mein Auto: 2001 740iL
Sorry Jason I meant a wheel bearing
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  #11  
Old 06-26-2014, 05:00 PM
edognight edognight is offline
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Mein Auto: 1997 e38. schwartzx2
horrible noise updated

so, after a year of a fixed driveline, I blew out the center support bearing that I fixed in the posts above. Again. Something tells me there is something wrong with the driveshaft itself, so I will get a new one.

I did pre stress it 5mm forward, and it was a cheap one, but it should last more than 1000 miles.

The reason I think it is the driveshaft is the u joint has two axes, and when I had the shaft off last year, one axis was very tight, and the other very loose. I thought nothing of it at the time, but the u joint has to be bad, if the resistance isn't equal, or at least that's my best guess.

Anyone have experience and can say for sure?
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  #12  
Old 06-28-2014, 07:06 AM
edognight edognight is offline
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Update

So, in the end, the drive shaft was bad, it would rotate easily in one direction and not in the other, should have known better. I picked up a new one at the bone yard, and it is smooth and easy in both axes, and no play whatsoever. New Guibo, new CSB good to go, and lesson learned.
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  #13  
Old 06-28-2014, 01:27 PM
Splitdog Splitdog is offline
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Location: Los Angeles
 
Join Date: Nov 2009
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Mein Auto: 2001 740iL
And you have to be careful with those. I dropped a drive shaft from about 6 inches and thought nothing of it. The car had a horrible shuddering. I was lucky that I mentioned that I dropped it to the tranny guy, he said to take it out and rebalance it. I did, and that was the problem.
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