BMW X-Drive Front LSD Differential

[shushikiary]

Alright, alright, I'll bump us to 19.


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19 shushikiary

I also agree about upgrading xdrive, not removing it. Not only have I found the torque vectoring to be great, I dont have traction issues like everyone else RWD has even at 600whp, its great in the snow, and it takes a lot of force off the drive train by spreading it over 2-4 axles instead of 1-2, and 2 drive shafts instead of 1.

 

[Cheezy]

If I sign, does the 50% deposit need to be sent today or whenever there's 30 confirmed buyers?

 

[Twisted Tuning]

If I sign, does the 50% deposit need to be sent today or whenever there's 30 confirmed buyers?

deposit will be once everyone is confirmed.



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[BriGuy]

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[Twisted Tuning]

good deal, getting there. I reached out to @MFactory about the possibility of moving forward with just 20. Havent gotten a response yet. I'll try sending another email, i know they are busy.


Current List:

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[MFactory]

When did you send the email? Could you resend please: myip @ teammfactory . com (without the spaces)

 

[Twisted Tuning]

When did you send the email? Could you resend please: myip @ teammfactory . com (without the spaces)

Lol. Wow, somehow i sent the email to myself this last time, haha. Just resent to you.

 

[MFactory]

Ok guys, I just need to confirm a few things as someone mentioned there was a "bolted" version?

1) If we make an LSD only, this actually only requires 10 sets (at the original $999.95 price). We would need a "bolted" oem sample to take measurements from though. I believe someone posted this up earlier in the thread? Of course, this is of no use to those who are "welded" though, unless they wanted to try find a "bolted" front diff from a breakers/scrapyard?

2) If we can get the "bolted" sample (will need both the diff and ring & pinion to verify measurements), I will check to see if the overall dimensions are the same as the "welded" sample that we have here. If it is, then we only need to make the 1 LSD that will work with both fitments.

3) For the "welded", we would still need to make a ring & pinion. For this, we originally required 30 sets, but if we can get 20 sets @ $1500 (inc. LSD), I will foot the bill myself and keep the extra 10 sets as stock

4) Someone also mentioned that the AT and MT are different ratios (I'm talking about the front ratios, not the rear)? If so, that introduces another problem; A new ratio means an entirely new ring & pinion = min. 20 sets

 

[shushikiary]

Given that the auto and the manual do have different rear ratios, and that the front and year have the same tire OD, and that the transfer case requires the front and rear to be within 1% rotationally or else the system complains... We can know that the autos and manuals have different front diff gear ratios as well.

So yes, we'd have to make a different gear set for front and rear.

From looking at the setup it seems the front is driving the gears on the drive side? aka its a high pinion setup? Anyways, that might find making an already existing gear set harder.

Are we sure no one makes gears that will fit? I'd be willing to bet given the expense of making custom gears that BMW used some common manufactured gear set. If so, we should just be able to get those, no? I could be wrong.

For sure if we have to make gears we'll need 2 different ratios, one for manual and one for auto though, no way around that.

I know that in the rear the ring gear is welded on all vehicles production date march 2007 and newer (manuals at least, not sure about auto's). Manual is 3.08, auto is 3.46. On option for manual peoples is to switch to 3.46 front and rear at the same time (which I'm not a fan of).

In this thread however https://www.e90post.com/forums/showthread.php?t=305069 they mention separating the welded ring gear. This may very well be an option, no? Then we don't have to even have gears made, we could send in our front diff currently (or find a used one as a core) and send it in to have the ring gear removed and drilled/tapped so it can be bolted on, and then we'd be set.

 

[MFactory]

It's more expensive to do the machining work than it is to just make a new ring & pinion.

It's not just separating the ring gear:

1) Cut off the ring gear
2) Machine the ring gear flat
4) Machine bolt holes into ring gear
5) Measure overall height to see how big of a spacer needs to be made so that the ring gear sits at the correct height
6) Machine a spacer
7) Labour to do all this

 

[shushikiary]

Here's a nice layout of what years and what manual/ auto / dtc had for gear ratio and welded, not welded (for the rear):

Thus..... making the auto 3.46, because they are all bolted... would be the easiest... but it would also mean that all manual xi owners would have to swap their rear diff to an auto 3.46 (might as well go LSD as well), and then of course change the speedo reporting speed calculation in the ECU.

The good news I hope, is that its unlikely they switched the carrier sizes (which they really refer to as housing type above) on the front diff. There wouldn't be room to go bigger and I doubt they would want to go smaller. So there shouldn't be a change in carrier size between auto/manual on the front diff I hope.

 

[MFactory]

This is the rear diff, so not applicable to the front.

It's also slightly wrong, as the 335d 2006-03/2007 is also bolted

 

[shushikiary]

Correct the chart is the rear only... I dont know, but would suspect, that if its welded in the rear its welded in the front, but I don't have anything to verify that.

 

[MFactory]

Yes, that could possibly be true and would make sense. Almost all BMW diffs now are welded which is a big pita

 

[shushikiary]

Yea the last thing I need is to up the ratio in my diffs (I'm an XI manual, 2008... so this all applies to me.. joy). I really don't need to be breaking axle shafts left and right up front from wheel hop (though hopefully the LSD would help with that) (GC lite 2.0's at 600 whp/wtq).

So for my self, I really don't want to have to switch away from 3.08.... but if that ends up being the only option to go to 3.46 I'll just swap both front and rear for helical LSD's at the same time and be done with it.... /sigh I really also dont want to up my 6th gear cruise RPM at 80mph, its already just above 3k, at 3.46 it would be almost 3400 or so.

 

[Twisted Tuning]

Looks like its all the same Housing with either a 3.46 or 3.08 in the diff housing for the front. Outside the little chart posted, i cannot find any "BMW" sourced information on whether or not, moreso which models had Welded for Bolted front diff.

One could assume as stated that if the rear is bolted or welded, then the front should follow suit. But OEM does stupid things sometimes. So impossible to be sure.

 

[scrllock]

After breaking in their rear LSD for a few weeks, I think I'm in, I assume most are 3.46 since MT xdrives seem rare? A/T here, so probably small and bolted, definitely 3.46. Will this come with a shim/bearing kit?

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[Cheezy]

Assuming it's the one @Twisted Tuning sent you, the welded sample that you have, @MFactory , came from an Automatic 2009 535i xdrive with a 3.46 rear gear. So that fact kills that chart that says all autos were bolted. But I'm going to ask the master tech at the local dealership if there's and literature on these front diffs

 

[shushikiary]

The chart is for the rear diff.


Given the chart doesn't say anything about the 535 we can't say its wrong, unless we know for a fact that the 535 rear diffs fallowed the same rules as the 135 and 335's did. If that's the case (key word there being IF), then what you're saying disproves the hypothesis that if the rear diff is bolted then the front diff is likely bolted, because then the rear diff for the 535 auto would be bolted, but the front welded.... but again we can't say that because we don't have a complete data set.

 

[MFactory]

Yes, the 535i's follow the same convention as the 135i/335i. If it's an E6X AT, then the "rear" is 100% bolted

If the front diff that I have is from an AT 535i, then yes, that confirms that the front diff does NOT follow the rear