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Thread: Driveshaft parts question

  1. #1
    Join Date
    Oct 2004
    Location
    Bay Area, CA
    Posts
    261

    Default Driveshaft parts question

    Hey guys, a while ago I posted a question about my car shaking and I found the center bearing to be cracked. When i finally removed the driveshaft today, the center bearing was MUCH worse than I had thought and the rubber was brittle and was no longer in contact with the metal support.

    Now my car has no guibo - its a little u-join to the tranny plate. but the back of the driveshaft has a CV joint and it easily moves to near extreme angles and im not sure if this is normal. I dont see cracks or anything, but could this contribute to the vibrations? I'd hate to reassemble this and find the same problem again.

    Thanks!

  2. #2
    Join Date
    Jan 2004
    Posts
    296

    Default

    Replacing a bad center bearing should do a lot to fix a shaking driveshaft.

    What do you consider an extreme angle? The CV joint needs to move to somewhat of an angle to be able to remove the shaft. If the boot is still intact and sealed it is probably fine. The CV joint costs 5-10 times more to buy a rebuilt driveshaft than to fix the center bearing. It likely would be making noise if it is bad.
    DanH
    1989 535iA 254k Miles
    1992 535iM 330k Miles

  3. #3
    Join Date
    Oct 2004
    Location
    Bay Area, CA
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    261

    Default

    When the shaking first started happening, while reversing i heard a noise that sounded like metal slapping metal. It has since gone away and I am left with only shakes. Would that be the type of noise or would it be more of a groaning?

  4. #4
    Join Date
    Oct 2004
    Location
    Bay Area, CA
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    Default

    I know that when you disamble the driveshaft, it has to be put back together EXACTLY as it came apart or it can vibrate, but what about how it mounts up to the car? what if it doesnt go in exactly the way it came out? Can that cause shaking too?

    Thanks!

  5. #5
    Join Date
    Jan 2004
    Posts
    296

    Default

    That slapping noise you heard most likely was due to the driveshaft hitting the exhaust heatshield due to the center bearing being shot. The same thing occurred on mine before I replaced the bearing. It was a loud grinding sound.

    If the shaft is out of balance that could cause shaking too, among other things, such as failing rear suspension parts. Does the shake vary with the speed of the driveshaft?

    Quote Originally Posted by Hypr5
    When the shaking first started happening, while reversing i heard a noise that sounded like metal slapping metal. It has since gone away and I am left with only shakes. Would that be the type of noise or would it be more of a groaning?
    DanH
    1989 535iA 254k Miles
    1992 535iM 330k Miles

  6. #6
    Join Date
    Mar 2004
    Posts
    404

    Default

    Putting the driveshaft back together is just a matter of lining up the match marks you make prior to disassembly. These marks will let you put the splined connection back together in the exact same orientation. You should also match mark the front u-joint & trans output flange with a prick punch so they go together in the same orientation. Do the same thing where cv joint bolts to differential pinion flange. I'd consider replacing the trans mounts also. I'm not familiar with the M20, but on my M30 E34, the trans mounts had collapsed, from exhaust heat and age so they were about 3/8" shorter then the new ones. This doesn't seem like much but it does change the driveshaft angle, and increases the angle that the u-joint operates, which can contribute to driveline vibrations. This is particularly important on high mileage u-joints that have developed a "notch" in their range of movement. The new trans mounts and center bearing fixed a vibration I had and avoided a costly driveshaft replacement. I posted more detail on this, which should turn up via the search engine, if you're interested.

    Paul Shovestul



    Quote Originally Posted by Hypr5
    Hey guys, a while ago I posted a question about my car shaking and I found the center bearing to be cracked. When i finally removed the driveshaft today, the center bearing was MUCH worse than I had thought and the rubber was brittle and was no longer in contact with the metal support.

    Now my car has no guibo - its a little u-join to the tranny plate. but the back of the driveshaft has a CV joint and it easily moves to near extreme angles and im not sure if this is normal. I dont see cracks or anything, but could this contribute to the vibrations? I'd hate to reassemble this and find the same problem again.

    Thanks!
    Last edited by Bellicose Right Winger; 01-13-2005 at 08:46 AM.
    .....Got to keep the loonies on the paath.

  7. #7
    Join Date
    Oct 2004
    Location
    Bay Area, CA
    Posts
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    Default

    Thanks for the reply.

    Apparently I didnt notice this before, but when the u-joints are PERFECTLY centered, it feels as if there is a notch there, is this call for replacement? they swivel smoothly otherwise.

  8. #8
    Join Date
    Mar 2004
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    I wouldn't worry about the notch as long as there is no play in the u-joint. I've found the notch on all (4) high mileage BMW driveshafts I've removed. But the notch could be a problem if the driveshaft angle is such that rotation of the driveshaft causes the u-joint to operate outside the narrow range of the notch. Changing the trans mounts on my car restored the proper angles and eliminated the vibration I had. 26K miles later all is vibration free.

    Paul Shovestul


    Quote Originally Posted by Hypr5
    Thanks for the reply.

    Apparently I didnt notice this before, but when the u-joints are PERFECTLY centered, it feels as if there is a notch there, is this call for replacement? they swivel smoothly otherwise.
    .....Got to keep the loonies on the paath.

  9. #9
    Join Date
    Feb 2004
    Posts
    558

    Default Question Paul, do you have any experience with...

    driveshafts with serviceable u-joints? BMP sells them but don't know how much. I recently checked the driveshaft in my car and found some play. The driveshaft has been replaced once and was thinking about getting the one where you can service the u-joints.

    Anyone have any experience with these BMP driveshafts?


    Quote Originally Posted by Bellicose Right Winger
    I wouldn't worry about the notch as long as there is no play in the u-joint. I've found the notch on all (4) high mileage BMW driveshafts I've removed. But the notch could be a problem if the driveshaft angle is such that rotation of the driveshaft causes the u-joint to operate outside the narrow range of the notch. Changing the trans mounts on my car restored the proper angles and eliminated the vibration I had. 26K miles later all is vibration free.

    Paul Shovestul

  10. #10
    Join Date
    Mar 2004
    Posts
    404

    Default

    Hector,
    Fortunately I've never had to replace a driveshaft. Sorry to hear you may have worn out a second one. Is play the only symptom or do you have vibration issues also? Any chance the play you detect is really in the transmission or differential? I thought most of the rebuilders like Portland Driveline and the one in Atlanta used serviceable u-joints.

    Paul Shovestul




    Quote Originally Posted by Hector
    driveshafts with serviceable u-joints? BMP sells them but don't know how much. I recently checked the driveshaft in my car and found some play. The driveshaft has been replaced once and was thinking about getting the one where you can service the u-joints.

    Anyone have any experience with these BMP driveshafts?
    .....Got to keep the loonies on the paath.

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