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Thread: Can an E39 M5 front suspension, including subframe, be used in a 540i 6-speed Sport?

  1. #1
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    Can an E39 M5 front suspension, including subframe, be used in a 540i 6-speed Sport?

    I have a bent front subframe in my 2002 540i Sport and have found a used M5 full front suspension, including subframe.

    I know that the E39 M5 and 540i front subframes (front axle support/wishbone) have different part numbers, 31112228790 for the M5 and 31111092157 for the 540i.

    I believe that all the other suspension components other than the struts and swaybar are identical.

    But are the two subframes interchangeable? Can I use the M5 subframe in my 540i? I'm wondering if the M5 subframe is just heavier or does it have different attachment points for the engine mounts since the engine is different? Some other difference in the geometry?

    So the bottom line is that can I use the M5 front suspension as a donor to repair my 540i suspension? (I'll adding new Bilstein struts also.)

    Thanks for any insights or advice you all can offer.
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  2. #2
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    I'm going to go out on a limb and say yes.

    I would cross reference the mounting hardware part numbers and see if they have the same numbers/length just to double check. Since as you said all the other suspension bits are essentially the same, and IIRC you can interchange an I6 to V8 subframe... I don't see why they would change the M5 drastically from the 540i.

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  3. #3
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    Quote Originally Posted by Justin517 View Post
    I'm going to go out on a limb and say yes.

    I would cross reference the mounting hardware part numbers and see if they have the same numbers/length just to double check. Since as you said all the other suspension bits are essentially the same, and IIRC you can interchange an I6 to V8 subframe... I don't see why they would change the M5 drastically from the 540i.
    I'm not sure what you mean about IIRC interchanging I6 to V8? What's IIRC? Both the 540i and M5 are V8's but I don't know if they use the same block or whatever... never looked it up!
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  4. #4
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    Quote Originally Posted by M3inSC View Post
    I'm not sure what you mean about IIRC interchanging I6 to V8? What's IIRC? Both the 540i and M5 are V8's but I don't know if they use the same block or whatever... never looked it up!

    IIRC means If I recall correctly.


    All I know about this is that the I6 rack-and-pinion steering box will NOT fit under an M62. That being said, I know an M5 steering box will bolt onto a 540i. I would imagine that an M5 subframe would work, but an I6 frame wouldn't. The I6 and V8 ones are different, too. The I6 is rectangular aluminum beams and the V8 has black, tubular beams.


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  5. #5
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    IIRC - if I remember correctly.

    There was only one E39 body structure built at the factory and it will accept all cradles, but the cradles are engine-specific. You'll need to go through RealOEM and check to see if the mounting bolts, heat shields, and other parts attached to the cradle are the same for a 540i and M5.

    While the suspensions are identical between 540i and M5, the major problem may be whether they share the same engine mount locations. You'd have to take measurements on both of them to find out. Trying to source a 540i cradle might be easier, there were more of them built and likely dont command a higher price like an M5 part will.

  6. #6
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    An s62 will physically bolt into a 540i so I think that answers that question.

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  7. #7
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    Quote Originally Posted by ElleShooTiger View Post
    IIRC - if I remember correctly.

    While the suspensions are identical between 540i and M5, the major problem may be whether they share the same engine mount locations. You'd have to take measurements on both of them to find out. Trying to source a 540i cradle might be easier, there were more of them built and likely dont command a higher price like an M5 part will.
    That is exactly what I was thinking would be the difference. Interestingly enough though, there are more M5 subframes available and they are cheaper! That's why I was wondering if I could use the whole M5 front suspension, including the subframe to repair my 540i front suspension.

    In reply to the earlier post, of course the 6 cylinder e39's have a different subframe than the V8 540i and M5!

    - - - Updated - - -

    Quote Originally Posted by Justin517 View Post
    An s62 will physically bolt into a 540i so I think that answers that question.
    Yes, it would seem too. Then the only reason for a different part number would be that the M5 subframe is heavier/stronger or something like that, because of the extra power in the S62?
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    only difference is the motor mounts an sway bar and the springs and shocks. its essentially the same thing.
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  9. #9
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    Quote Originally Posted by TriniSpeC View Post
    only difference is the motor mounts an sway bar and the springs and shocks. its essentially the same thing.
    Yes, I re-checked the part numbers on RealOEM and it looks like that is correct. So I am concluding that the only difference in the front subframe is that using the M5 subframe in a 540i would require also using the M5 motor mounts.

    Also then, in response to one of the responses above, if you were to drop an M5 S62 engine into a 540i, you would have to change the motor mounts also. Presumably because of the higher torque in the S62 engine?
    Last edited by M3inSC; 04-23-2013 at 11:02 AM.
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  10. #10
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    Quote Originally Posted by M3inSC View Post
    That is exactly what I was thinking would be the difference. Interestingly enough though, there are more M5 subframes available and they are cheaper! That's why I was wondering if I could use the whole M5 front suspension, including the subframe to repair my 540i front suspension.

    In reply to the earlier post, of course the 6 cylinder e39's have a different subframe than the V8 540i and M5!

    - - - Updated - - -


    Yes, it would seem too. Then the only reason for a different part number would be that the M5 subframe is heavier/stronger or something like that, because of the extra power in the S62?
    There is quite likely no physical difference between the M5 part and the 540i part. The guibo, CSB and rear prop-shaft CV joint also have different numbers but I have held both in my hand and cannot tell any difference, they even weigh exactly the same... if the CSB and guibo were made of stiffer rubber it would have to be denser and weigh more, even if just slightly, I used a scale that is good down to .1g.

    I honestly think they assigned some of the M5 parts different numbers simply so they know to charge more for them.
    Last edited by Justin517; 04-23-2013 at 12:10 PM.

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  11. #11
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    Quote Originally Posted by Justin517 View Post

    I honestly think they assigned some of the M5 parts different numbers simply so they know to charge more for them.
    LOL! That makes the most sense of all!
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  12. #12
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    so what is different in the M5 rear subframe and suspension that the 525 530 540 don't have. I'm building my 525it M54 to around 400hp and was looking to install a full subframe,suspension and brakes from a M5. I know they will bolt up to the body but what is the difference in the frame or suspension parts.

  13. #13
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    Rear - different story - there is no e39 M5 wagon - you will need the diff and axles for sure.

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    Quote Originally Posted by albertjwood View Post
    so what is different in the M5 rear subframe and suspension that the 525 530 540 don't have. I'm building my 525it M54 to around 400hp and was looking to install a full subframe,suspension and brakes from a M5. I know they will bolt up to the body but what is the difference in the frame or suspension parts.
    Touring and sedan rear subframes are quite different and not interchangeable, but the suspension arms, ball joints, axles, diffs, bushings, etc. are all the same and are interchangeable. I don't mean the diffs themselves are the same, but the mounting locations are and you can swap a M5 diff into a Touring rear subframe. You'll need to massage the brace behind one of the diff mounting points as the bolt head can tend to rub it or even dig into it, but that's easy to do. Basically, if your current rear suspension arms and such are fairly new, there won't be any benefit of going to M5 parts. Brakes are an upgrade, but require a bit of modification or replacement of the brake rotor backing plates to fit them and either replacing the wheel bearings with M5 bearings or opting to not use set screws on the rear rotors since the holes don't line up to the M5 rotors.

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