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Thread: Mystery Subsonic vibration... where to look?

  1. #1
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    Mystery Subsonic vibration... where to look?

    So I've been searching but haven't found anything yet.

    Basically for the first, say, 15 minutes of my drive I have a bad, what I would describe as a subsonic vibration. It seems to be worst between 30-40MPH. It feels like tires that have flat spots. But it's not tires, I have put two different sets, with different rims on it. It's definitely tied to road speed. I've also notices that I have some drive line slop as I can feel a small clunk when on and off th accelerator. I've parked the car now that I have confirmed that its not the tires as I want to get underneath it as its a pretty bad vibration.

    I'm thinking either flex disks (guibos) or a CSB issue... but if there are any other spots I should check while I'm underneath it I'm totally open to suggestion. It just baffles me that it seems to go away, or at least lessen after the driveline has "warmed up"

    thoughts????
    Last edited by dude99; 03-26-2019 at 09:34 PM.

  2. #2
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    It sounds like symptoms of a failing CSB. Have to crawl under with a flashlight and start wiggling stuff. Might also be related to a failing rear axle CV joint?

  3. #3
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    probably CSB or flex disc, but check everything rubber. Motor and trans mounts and diff bushings.

  4. #4
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    kk, thanks for letting me know I'm at least heading in the right direction. Hopefully I'll have some time to get it up on jack stands and take a peak tomorrow.
    1983 BMW 733i My current project (or at least one of them)
    2003 Volvo V70 5 Speed Current Daily Driver
    1993 300TE 4Matic Project wagon -sold
    1997 E290 Turbo Diesel Wagon -traded for above, an amazingly comfortable car to drive, great drivetrain, but the rust, oh my god the rust

    1992 BMW 525i -traded in
    1990 Silver 300TE -Sold Loved the wagon, hated the M103
    1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
    1979 Silver 300D "The Silver Slug" -Sold

  5. #5
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    DIdn't have a lot of time over the weekend, but I threw it up on some jack stands quickly and had a peak. Nothing seems loose, axel shafts seem fine and no split boots, front flex disk is fine, trans mount looks fine. I didn't have time to drop the exhaust to pull all the heat shields to examine the CSB, but since its the only part I didn't see, its probably the cause....
    1983 BMW 733i My current project (or at least one of them)
    2003 Volvo V70 5 Speed Current Daily Driver
    1993 300TE 4Matic Project wagon -sold
    1997 E290 Turbo Diesel Wagon -traded for above, an amazingly comfortable car to drive, great drivetrain, but the rust, oh my god the rust

    1992 BMW 525i -traded in
    1990 Silver 300TE -Sold Loved the wagon, hated the M103
    1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
    1979 Silver 300D "The Silver Slug" -Sold

  6. #6
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    Will a bad CSB look visibly bad, or do I need to plan to drop the driveshaft to assess its health?

  7. #7
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    So the CSB and holder was only 30 Canadian pesos shipped to my door, I figured for the work to get in there and inspect it, I may as well change it since it doesn't look terrible hard to do so. That being said, are there any tips\tricks I should be aware of? I read somewhere that you had to preload it somehow?
    1983 BMW 733i My current project (or at least one of them)
    2003 Volvo V70 5 Speed Current Daily Driver
    1993 300TE 4Matic Project wagon -sold
    1997 E290 Turbo Diesel Wagon -traded for above, an amazingly comfortable car to drive, great drivetrain, but the rust, oh my god the rust

    1992 BMW 525i -traded in
    1990 Silver 300TE -Sold Loved the wagon, hated the M103
    1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
    1979 Silver 300D "The Silver Slug" -Sold

  8. #8
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    Cple of things first-
    I'd use an e34 csb, heavier duty and make sure it's orientated correctly when installing it.
    Pretty straight forward job, drop exhaust, pull heat shield and remove driveshaft. You'll have to separate the driveshaft so make sure you mark it well when you separate it as it's balanced, if you don't mark it it'll cause driveshaft vibrations.
    Surclip holds csb in once driveshaft is separated.
    I'd replace guibo too while you're in there.
    Preloading is easy, once it's all together, driveshaft bolted in and both csb bolts in place loose, push the bearing forward a bit (towards the front of the car) and tighten the bolts.
    On jackstands it's a 1/2 day job +-, on a lift I've done it in a few hours and that included a rear diff mount.
    Last edited by kojo96; 04-08-2019 at 12:10 AM.

  9. #9
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    Good to know, but sadly I already ordered the e23 bearing. No lift so I'll plan on a full day since I have a bum elbow.

    thanks for all the info
    1983 BMW 733i My current project (or at least one of them)
    2003 Volvo V70 5 Speed Current Daily Driver
    1993 300TE 4Matic Project wagon -sold
    1997 E290 Turbo Diesel Wagon -traded for above, an amazingly comfortable car to drive, great drivetrain, but the rust, oh my god the rust

    1992 BMW 525i -traded in
    1990 Silver 300TE -Sold Loved the wagon, hated the M103
    1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
    1979 Silver 300D "The Silver Slug" -Sold

  10. #10
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    Quote Originally Posted by kojo96 View Post
    Cple of things first-
    I'd use an e34 csb, heavier duty and make sure it's orientated correctly when installing it.
    Pretty straight forward job, drop exhaust, pull heat shield and remove driveshaft. You'll have to separate the driveshaft so make sure you mark it well when you separate it as it's balanced, if you don't mark it it'll cause driveshaft vibrations.
    Surclip holds csb in once driveshaft is separated.
    I'd replace guibo too while you're in there.
    Preloading is easy, once it's all together, driveshaft bolted in and both csb bolts in place loose, push the bearing forward a bit (towards the front of the car) and tighten the bolts.
    On jackstands it's a 1/2 day job +-, on a lift I've done it in a few hours and that included a rear diff mount.
    Thanks for this explanation kojo. I've been wondering how to do this for quite a while.

    When you say a bit, any guidance on how many mm that is? Is it possible to push it too far? Can you just push it as far as it will go forward? Or is somewhere between dead center and all the way forward the best?

    Thanks very much!
    Chad

  11. #11
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    So, I've been doing a lot of reading about this on the e28 side of things, and I'm wondering how many people here have found their U-Joint to be trashed as well? It seems on the e28 its bad U-joints that cause the CSB to fail. Am I setting myself up for failure here by not planning to replace it?
    1983 BMW 733i My current project (or at least one of them)
    2003 Volvo V70 5 Speed Current Daily Driver
    1993 300TE 4Matic Project wagon -sold
    1997 E290 Turbo Diesel Wagon -traded for above, an amazingly comfortable car to drive, great drivetrain, but the rust, oh my god the rust

    1992 BMW 525i -traded in
    1990 Silver 300TE -Sold Loved the wagon, hated the M103
    1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
    1979 Silver 300D "The Silver Slug" -Sold

  12. #12
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    If the U joints don't feel notchy or have end play I'd reuse them. They are pretty durable.
    Steve H.

  13. #13
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    Quote Originally Posted by cfisher535is View Post
    Thanks for this explanation kojo. I've been wondering how to do this for quite a while.

    When you say a bit, any guidance on how many mm that is? Is it possible to push it too far? Can you just push it as far as it will go forward? Or is somewhere between dead center and all the way forward the best?

    Thanks very much!
    Chad
    I pushed it forward just a bit, didn't really measure but I watched as the rubber center moved slightly forward, many miles since and no issues.

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