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E46 Xi Forum
The E46 XI was produced from 01-05 in sedan and touring body styles. Powered by either a 2.5L inline 6 in the 325xi or a 3.0L inline 6 330xi. Discuss all thing about BMW AWD E46 'Xi' here.

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Old 11-19-2011, 12:46 PM   #1
redbull 325is
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swapping in LSD rear diff questions

I have a donor LSD differential from an e36 m3. I was thinking of taking the limited slip unit out of it and installing it in my e46's rear end (with new bearings, seals etc at a drivetrain shop).

Any ideas if this would negatively affect the drive train or traction control systems?

Thanks!
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Old 11-19-2011, 12:58 PM   #2
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Originally Posted by redbull 325is View Post
I have a donor LSD differential from an e36 m3. I was thinking of taking the limited slip unit out of it and installing it in my e46's rear end (with new bearings, seals etc at a drivetrain shop).

Any ideas if this would negatively affect the drive train or traction control systems?

Thanks!
Really? You will destroy your drive train almost instantly due to having two different gear ratios. Your abs will need to be disabled your dsc will need to be disabled. list goes on and on
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Old 11-19-2011, 01:39 PM   #3
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Really? You will destroy your drive train almost instantly due to having two different gear ratios. Your abs will need to be disabled your dsc will need to be disabled. list goes on and on
just taking the LSD unit, not the gear (they are bolted together).. why would abs and dsc be negatively affected?
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Old 11-19-2011, 02:22 PM   #4
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Originally Posted by redbull 325is View Post
I have a donor LSD differential from an e36 m3. I was thinking of taking the limited slip unit out of it and installing it in my e46's rear end (with new bearings, seals etc at a drivetrain shop).

Any ideas if this would negatively affect the drive train or traction control systems?

Thanks!


OP, maybe you know something I don't.

Question: Since when does an E36 LSD fit into ANY E46 diff pumpkin ?


Please let us know.
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Old 11-19-2011, 04:19 PM   #5
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Okay for reasonable understanding - if conventional DSC uses logic to "grab" brakes on the spinning side to transfer energy to the opposing wheel, then under the same spinning condition, the superior LSD would be mechanically performing its transfer method internally. Should DSC continue knocking on the door, grabbing brakes, the LSD would not operate efficiently. Wheel sensors continue sending data to the DSC to process where the affect may go crazy with LSD attempting to do its job.

Perhaps there is a DSC program that could "understand" the different parameters an LSD needs to operate under? And then there's the front open diff that fights with the rear if their ratios differ. Ideally, everything is swapped to LSD. Easy, buy a WRX. This is a lot of R&D that never happened with our cars. Don't mess with the German engineers here, it could be an exercise in futility.
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Old 11-19-2011, 05:20 PM   #6
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^No.

You can put an LSD in the rear of an xi no problem, provided it's the same ratio as the front diff.
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Old 11-19-2011, 05:53 PM   #7
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.....You can put an LSD in the rear of an xi no problem, provided it's the same ratio as the front diff.

Totally agree.


But, I still say there's NO way in hell that an E36 LSD fits into the diff pumpkin of an E46.

Only an E46 LSD fits into the E46 diff pumpkin.
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Old 11-19-2011, 05:59 PM   #8
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^No.

You can put an LSD in the rear of an xi no problem, provided it's the same ratio as the front diff.
And there would be no interaction with DSC? I still think DSC will attempt to override the LSD creating strange results. Has this swap been pulled off?
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Old 11-19-2011, 06:22 PM   #9
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And there would be no interaction with DSC? I still think DSC will attempt to override the LSD creating strange results. Has this swap been pulled off?
I hear what your saying.

But I see no difference between the Xi & my 330Ci in terms of any traction control relating to an LSD.

I have a Quaife LSD in my 330Ci, the DSC barely comes on now. They certainly don't fight each other.
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Old 11-19-2011, 06:30 PM   #10
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Totally agree.


But, I still say there's NO way in hell that an E36 LSD fits into the diff pumpkin of an E46.

Only an E46 LSD fits into the E46 diff pumpkin.
I thought all medium case BMW diffs had interchangeable internals..?

[edit]
quick search yields that they are similar... up to e36
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Old 11-19-2011, 06:43 PM   #11
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I thought all medium case BMW diffs had interchangeable internals..?

[edit]
quick search yields that they are similar... up to e36

That's right.

So you need to buy an E46 LSD, & the cheapest one is the Quaife for about $1350.
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Old 11-19-2011, 07:05 PM   #12
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I hear what your saying.

But I see no difference between the Xi & my 330Ci in terms of any traction control relating to an LSD.

I have a Quaife LSD in my 330Ci, the DSC barely comes on now. They certainly don't fight each other.
Interesting. With that, I'm rethinking the internal behavior of the LSD may be so efficient that DSC response doesn't occur countering the affect. Wheel side to side energy transfer may be smooth and subtle not demanding a "grab" response.

Good discussion.
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Old 11-19-2011, 07:30 PM   #13
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I completely disagree, if you put an lsd rear even if it's the same ratio. Under hard driving the dsc will get confused. It will try to lock both wheels as it will see them both spinning. This doesn't happen on a open diff. You will need to remove your dsc which means your abs. Furthermore to elaborate on the difference between ci and xi. You don't have a variable output T/C between your diff/tranny. I can assure you it won't work. I only have 2 wheel speed sensors on my car (rears, too lazy to rewire fronts) When the ABS brain is plugged in, It constantly pulses the brakes making it very hard to move the car.

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Old 11-19-2011, 08:12 PM   #14
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That's right.

So you need to buy an E46 LSD, & the cheapest one is the Quaife for about $1350.

can you rob the internals of an e46 m3 unit?
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I completely disagree, if you put an lsd rear even if it's the same ratio. Under hard driving the dsc will get confused. It will try to lock both wheels as it will see them both spinning. This doesn't happen on a open diff. You will need to remove your dsc which means your abs. Furthermore to elaborate on the difference between ci and xi. You don't have a variable output T/C between your diff/tranny. I can assure you it won't work. I only have 2 wheel speed sensors on my car (rears, too lazy to rewire fronts) When the ABS brain is plugged in, It constantly pulses the brakes making it very hard to move the car.
limited slip diffs act the same as an open diff during normal driving, so in that regard dsc won't "notice" the difference. Now during excessive wheel spin situations is where there could be some issues, I see is specifically as a front to rear issue.
I wonder how it would deal with this on mud or snow for instance where there isn't enough drag to break the static friction of the clutch packs in the rear diff, you will have a situation of 2 rear wheels have restistance versus one front wheel. Since or TC goes for the path of least resistance will it just spinning one of the front wheels?
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Old 11-19-2011, 08:17 PM   #15
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can you rob the internals of an e46 m3 unit?


limited slip diffs act the same as an open diff during normal driving, so in that regard dsc won't "notice" the difference. Now during excessive wheel spin situations is where there could be some issues, I see is specifically as a front to rear issue.
I wonder how it would deal with this on mud or snow for instance where there isn't enough drag to break the static friction of the clutch packs in the rear diff, you will have a situation of 2 rear wheels have restistance versus one front wheel. Since or TC goes for the path of least resistance will it just spinning one of the front wheels?
I don't understand? What is the need of an lsd if you aren't going to drive it hard enough to enjoy it? Sure you granny the car around with your lsd the dsc will rarely have issues. If you are driving the sh!t outta your car and having wheel spin (where the lsd/dsc/ will fight) what is the point?
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Old 11-19-2011, 08:20 PM   #16
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I don't understand? What is the need of an lsd if you aren't going to drive it hard enough to enjoy it? Sure you granny the car around with your lsd the dsc will rarely have issues. If you are driving the sh!t outta your car and having wheel spin (where the lsd/dsc/ will fight) what is the point?
Not really the point I was trying to illustrate
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Old 11-19-2011, 08:25 PM   #17
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Not really the point I was trying to illustrate
Happy modding I say do it, it's awesome and will be epic. Take pics!
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