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Thread: Any suggestion what else to do while servicing the differential mount bushing...

  1. #1
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    Any suggestion what else to do while servicing the differential mount bushing...

    Hi all,

    I am planning on removing the differential to service the mount bushing. And I had some questions that I wanted to run them by you guys.

    First question: is there any other items you would recommend while the diff is out and unmounted? The actual diff seems to be in good running condition so I don't think it needs to be rebuilt. But one of the inner axle boots is worn and rusted and looks like it could be serviced, and I will probably service all of them them. Is there anything else you would recommend?
    (Note: Trailing arm and subframe bushings were serviced. Subframe reinforcement is saved for another day.)

    Next question. Can the diff be unmounted without removing (or hanging) the exhaust? And has anyone been able to remove the diff cover without unmounting the diff? From what I've gathered and seen, it seems less-likely. But I wanted to find out if anyone was able to do it.

    TIA
    Last edited by nevan; 05-11-2018 at 02:02 PM.
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  2. #2
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    You need to remove the back section of exhaust and lower the subframe enough to clear the diff mount. Or drop the diff. The top 2 bolts holding diff to subframe are difficult to get to and generally require dropping the subframe. Given that starting the bolts back into the diff when trying to do so while Subframe is still in the car is probably the most stupidly simple but difficult thing to do, ever, I would drop the subframe with the diff still attached enough to remove the cover. FYI If you are swapping the diff cover bushing, DO NOT use anything but OEM. Harder bushings will do nothing but damage the mount/rear pan areas of the car.
    Dan "PbFut" Rose

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    You can install the stud kit from Condor, which will make reinstallation of the diff much easier.
    I wouldn't trust their torque specs, though - theyre too low.
    If the diff isn't leaking, I'd probably leave the rest alone.
    You can buy the bushing removal/install tool that allows you to remove the bushing without completely removing the diff.
    It's an absolutely beautiful and well thought out tool made by Bosch, but it will take 3 weeks to arrive from Germany. I bought it (83-30-0-492-179) from getbmwparts.com for $117 shipped.
    I bought it but on the second use the bushing was so stuck that I totally destroyed it.

    IMG_20180412_203407.jpg

    IMG_20180422_162517.jpg
    IMG_20180422_165325.jpg
    Last edited by scenturion; 05-11-2018 at 03:19 PM.

  4. #4
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    Replace all of o-rings (output shafts), lock ring...etc. Using a punch or something similar, mark how the driveshaft aligns with the pinion gear input. I did this when i had my differential out.
    Tony
    "You can't sign away negligence."

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    Quote Originally Posted by PbFut View Post
    You need to remove the back section of exhaust and lower the subframe enough to clear the diff mount. Or drop the diff. The top 2 bolts holding diff to subframe are difficult to get to and generally require dropping the subframe. Given that starting the bolts back into the diff when trying to do so while Subframe is still in the car is probably the most stupidly simple but difficult thing to do, ever, I would drop the subframe with the diff still attached enough to remove the cover. FYI If you are swapping the diff cover bushing, DO NOT use anything but OEM. Harder bushings will do nothing but damage the mount/rear pan areas of the car.
    Thanks, these really helps! I will most likely take the diff to a shop to get the bushings pressed in. I will be surely replacing with a oem bushing.

    - - - Updated - - -

    Quote Originally Posted by scenturion View Post
    You can install the stud kit from Condor[/URL], which will make reinstallation of the diff much easier.
    I wouldn't trust their torque specs, though - theyre too low.
    If the diff isn't leaking, I'd probably leave the rest alone.
    You can buy the bushing removal/install tool that allows you to remove the bushing without completely removing the diff.
    It's an absolutely beautiful and well thought out tool made by Bosch, but it will take 3 weeks to arrive from Germany. I bought it (83-30-0-492-179) from getbmwparts.com for $117 shipped.
    I bought it but on the second use the bushing was so stuck that I totally destroyed it.
    The Condor stud kit looks interesting, I will need to get more info. Thanks!

    - - - Updated - - -

    Quote Originally Posted by ProductUser View Post
    Replace all of o-rings (output shafts), lock ring...etc. Using a punch or something similar, mark how the driveshaft aligns with the pinion gear input. I did this when i had my differential out.
    Awesome, I added them to the list. Thanks!
    Last edited by nevan; 05-11-2018 at 08:05 PM.
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    As a counter point, I never drop the exhaust, and don't have any issues removing or installing the top bolts. Even the M with the spacer. I really hate messing with exhaust... I do transmissions and driveshafts without removing it. Lately the only times I remove the rear cans is to install Randy's kit.
    Last edited by rf900rkw; 05-11-2018 at 08:13 PM.

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    Why are you servicing the diff mount bushing? Is it because the bushing has failed, or as part of a maintenance schedule? If it is just as part of a schedule, but not broken, I say let it be. You don't say which Z3 you are doing this to, but if it's the ///M, and you are pulling the axles from the hubs, do yourself a favor and rotate axle shafts from side to side--they are the same and will last quite a bit longer that way, as they have worn all this time in the one direction (a trick from Randy F's play book). There is a special tool for pulling and reinstalling the axles into the hubs you may want to look into--it may be you don't need it, or it may be essential--could go either way.

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    Good to know. I wish I had done this when the diff was out. Maybe next time I need something to do...
    What do you recommend for popping the axles out of the hub? A sledge + punch didn't work on a buddy's Z3.
    Was thinking about one of these.
    Last edited by scenturion; 05-11-2018 at 10:08 PM.

  9. #9
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    Quote Originally Posted by rf900rkw View Post
    As a counter point, I never drop the exhaust, and don't have any issues removing or installing the top bolts. Even the M with the spacer. I really hate messing with exhaust... I do transmissions and driveshafts without removing it. Lately the only times I remove the rear cans is to install Randy's kit.
    Thank for the advise, Randy. I found additional sources to do this project without dropping the exhaust as you mentioned.
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    Quote Originally Posted by Mr Bingley View Post
    Why are you servicing the diff mount bushing? Is it because the bushing has failed, or as part of a maintenance schedule? If it is just as part of a schedule, but not broken, I say let it be. You don't say which Z3 you are doing this to, but if it's the ///M, and you are pulling the axles from the hubs, do yourself a favor and rotate axle shafts from side to side--they are the same and will last quite a bit longer that way, as they have worn all this time in the one direction (a trick from Randy F's play book). There is a special tool for pulling and reinstalling the axles into the hubs you may want to look into--it may be you don't need it, or it may be essential--could go either way.
    Thank for the tip on switching sides for the axle shafts, Mr Bingley. That is a great suggestion! I usually go by visual inspection. And I haven't noticed anything major. But I do feel the thumping sound shifting between 1-2-3 gears occasionally and gradually more . I will probably take time to gather a complete list of things to service then do them all at once.
    Last edited by nevan; 05-14-2018 at 07:09 PM.
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  11. #11
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    everytime I've used something like this, it's pulled the hub OFF the bearing inner race...

    Last time I pulled my half-shafts, I pulled them out of the diff-side, then just tapped the end of the axle on the hub-side with a dowel and a hammer.
    Pulling the axle back into the hub has always been a chore though
    Last edited by NLu; 05-14-2018 at 01:02 PM.

  12. #12
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    Quote Originally Posted by NLu View Post
    ...Last time I pulled my half-shafts, I pulled them out of the diff-side, then just tapped the end of the axle on the hub-side with a dowel and a hammer...
    +1

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    Quote Originally Posted by nevan View Post
    Thank for the tip on switching sides for the axle shafts, Mr Bingley. That is a great suggestion! I usually go by visual inspection. And I haven't noticed anything major. But I do feel the thumping sound shifting between 1-2-3 gears occasionally and gradually more . I will probably take time to gather a complete list of things to service then do them all at once.
    As recent as last night...


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    Quote Originally Posted by Randy Forbes View Post
    As recent as last night...

    That looks so good, Randy!! Definitely puts mine in shame.

    Another question for folks, has anyone heard of SureTrack Axles? How are their quality? They seem very affordable that I am tempted to replace the whole axles instead of servicing the boots. What do you think? Any thought would be appreciated.
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    Never heard of them, but I will wager they don't make M axles.


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    Do people actually replace the axle to diff bolts every time? They have serrated flanges, but I don't think theyre torque-to-yield?

  17. #17
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    Quote Originally Posted by scenturion View Post
    Do people actually replace the axle to diff bolts every time? They have serrated flanges, but I don't think theyre torque-to-yield?
    (no)

    If I encounter any that some hack let an impact gun/socket mangle the head, or if corrosion has gotten to them, I keep a set in stock for those occasions, Most of the time, I media-tumble them and they look as good as new; if there was any shortcomings in doing that__for the last fourteen (14) years__it would've shown up by now. Actually, more years than that, as I'd swap out the 3.15:1 for a 3.73:1 in my '01 with some frequency between '02 - '04 only replacing the bolts once.

  18. #18
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    Quote Originally Posted by PbFut View Post
    DO NOT use anything but OEM. Harder bushings will do nothing but damage the mount/rear pan areas of the car.
    Why do people spread this rumor? I've had three popped welds in my roadster for many years, and I swapped to a poly mount along with the sub-frame bushings. I drive like an ass, and nothing has gotten any worse in ~30k of hell. Also used poly in all 7 rear mounts of my coupe and guess what... No problems.
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    /.randy

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    Quote Originally Posted by rf900rkw View Post
    Owned by a middle-aged female lawyer.


    I guess she gets down


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  21. #21
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    Quote Originally Posted by GG///M3 View Post
    I guess she gets down


    Sent from my iPhone using Tapatalk
    Lol,

    Here is my latest update. A bit of setback actually...

    IMG_20180916_200557.jpg

    Good news is that diff mount bushing and the actual diff itself are in great condition.

    Bad news is that I need to figure out what to do with the diff cover now.

    I'm kicking myself for opting out the dual/single ear with Randy's reinforcement kit... And I have to improvise now...
    Last edited by nevan; 09-17-2018 at 12:21 PM.
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  22. #22
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    FWIW I had a similar crack in my spare diff housing fixed at a local welding shop for <$100.00.

    IMG_20180622_134213.jpg

    IMG_20180622_134208.jpg

    It's a bummer that you'll have to drop the diff and do it over, but its more time than money.

  23. #23
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    Quote Originally Posted by scenturion View Post
    FWIW I had a similar crack in my spare diff housing fixed at a local welding shop for <$100.00.

    IMG_20180622_134213.jpg

    IMG_20180622_134208.jpg

    It's a bummer that you'll have to drop the diff and do it over, but its more time than money.
    Thanks so much, scenturion. Your post brought hope back. I am talking with my welder so hopefully he will be able to fix it...
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    anybody using a poly diff bushing on a reinforced diff mount and trunkfloor?
    -Phil

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    Quote Originally Posted by Z-Thrizzle View Post
    anybody using a poly diff bushing on a reinforced diff mount and trunkfloor?
    As Phil mentioned, I am also curious if poly bushing would be a viable option (particularly with Randy's reinforcement kit). Could anyone with experience please chime in? TIA!
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