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Thread: Best diff upgrade for 540i 6 spd??

  1. #76
    Join Date
    Apr 2016
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    the great pacific n.w.
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    540it, 540sedan, 540-6 s
    No, no, and no.
    E39 M5 and E60 M5, are longer, so require an M5 length driveshaft. E60 CV is different from e39.
    E39 M5 Diffs can use E32 output flanges to use 540 axles, or M5 axles with the original M5 output flanges. E32 flanges are as expensive as buying axles.
    E60 M5 (M6) axle flanges are L+R and no known swap to other models. Every model has its own locking snap ring location. So again, M5 axles.
    Plus, An e39 rear cover. Those are getting expensive.
    Modifying costs, and aluminum welding=$$$. It's a doable swap, if you can do all that yourself.

  2. #77
    Join Date
    Jul 2019
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    Canada
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    633
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    BMW E39 528i 1998
    In that case we're no further ahead than where we started.

  3. #78
    Join Date
    Jan 2008
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    Arida Zona
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    30,282
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    z3
    E60 M5 diffs are different fitment than E60 V8 diffs.

    E60 M5 diff ratio is also very high because the E60 M5 revs very high, normally has 7 gears and it makes all its power up top. That ratio would not work well for an E39 V8 application.

    I also don't see any reason welding the front bracket on is required for a stock power application. The torque from acceleration will be pushing against the stronger part of the ear if drilled. Offset poly bushings could also possibly be made to install it without drilling anything.

  4. #79
    Join Date
    May 2018
    Location
    Cullowhee North Carolina
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    1,551
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    1999 323i/5 2002 540i/6
    I see no need to weld the additional bracket, I'm sure it was to eliminate the subframe cracking issues the e39 m5 in particular can have. It also seems odd having a part with massive load being applied be offset mounted. The diff mount bores are quite obviously just some extruded aluminum. You could probably find the right size off of McMaster carr. You can get brackets laser cut pretty cheap these days. If I find some extra time I might make the appropriate CAD files and drop them here so they are a public resource. Power to the people man!

    Sent from my SM-S901U using Tapatalk
    Last edited by seagreen323i; 05-05-2024 at 04:22 AM.

  5. #80
    Join Date
    Jul 2019
    Location
    Canada
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    633
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    BMW E39 528i 1998
    Quote Originally Posted by Iamthebull View Post
    Just found one in New York on eBay Motors

    https://www.ebay.com/itm/25604810473...Bk9SR-DHz8_MYw

    - - - Updated - - -

    Looking on Real OEM: https://www.realoem.com/bmw/enUS/par...&q=33101428572
    As all options have been exhausted, I just ordered this 3.15 diff. It was just under $800 CAD. If I'm going to be changing diff mount rubbers, I might as well change the diff. Next step is wavetrac. That's going to be about $1800 CAD, ouch!
    What else is there to do, E39 M5 diffs are so expensive, over $1000 USD without the drive shaft.
    Driveshaft flanges and driveshaft are at least another $1000 USD...
    So at that rate might as well buy a brand new wavetrac...

  6. #81
    Join Date
    Jul 2017
    Location
    Turkey
    Posts
    873
    My Cars
    '00 540i M-Tech
    3.15 is so useless for a DD car IMO. it's only good for a few fun moments but other than that makes zero sense. higher rpms @ highway means more consumption and higher noise.

  7. #82
    Join Date
    Jul 2019
    Location
    Canada
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    BMW E39 528i 1998
    Well if it drifts, maybe I can drift it then!
    Everyone to upgraded to 3.15 seems to love it.
    I found just the ring and pinion for 3.15 from E39 M5.
    I'm wondering if they'll fit into 2.81 diff to make it 3.15? I know M5 and 540i diffs are different size on the outside, but not sure about the ring and pinion.
    https://www.ebay.ca/itm/196253467790...mis&media=COPY

  8. #83
    Join Date
    Jul 2017
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    Turkey
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    '00 540i M-Tech
    Quote Originally Posted by Bmwe39528i1998 View Post
    Well if it drifts, maybe I can drift it then!
    Everyone to upgraded to 3.15 seems to love it.
    they probably love the LSD, not 3.15 I agree LSD is a must on these cars.

  9. #84
    Join Date
    Jan 2008
    Location
    Arida Zona
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    30,282
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    z3
    Quote Originally Posted by seagreen323i View Post
    I see no need to weld the additional bracket, I'm sure it was to eliminate the subframe cracking issues the e39 m5 in particular can have. It also seems odd having a part with massive load being applied be offset mounted. The diff mount bores are quite obviously just some extruded aluminum. You could probably find the right size off of McMaster carr. You can get brackets laser cut pretty cheap these days. If I find some extra time I might make the appropriate CAD files and drop them here so they are a public resource. Power to the people man!

    Sent from my SM-S901U using Tapatalk
    The idea of an offset bushing is just to make it a plug and play installation. I doubt an offset poly bushing would be any weaker in practice than drilling the front mounting ear. Probably paired best with poly rear diff bushings as well. May be a very small increase in NVH but with stock subframe bushings I doubt it'd be noticeable.

  10. #85
    Join Date
    Jul 2019
    Location
    Canada
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    633
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    BMW E39 528i 1998
    Two months since I created this post, 3.15 diff is here!




    The packaging was very poor and the lip got bent in a few places. Hopefully I can just unbend it.
    At least, and surprisingly, the diff's paint is all nice and clean with no rust! I don't need to sandblast and paint it, which is nice!

    Now just need to decide on then lsd

  11. #86
    Join Date
    Dec 2019
    Location
    KÝbenhavn
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    917
    My Cars
    1999 e39 520iA
    You can just replace the flange with yours.

    Sent from my SM-S918B using Tapatalk

  12. #87
    Join Date
    Jan 2008
    Location
    Missouri
    Posts
    737
    My Cars
    '02 540i/6
    Good luck with the upgrade!

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