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Discussion Starter #1
I have taken some interest in doing a worm gear lsd swap this fall. I know that no one here has done it, which is why I'm hoping that I can find out if there would be complications with doing this kind of swap. So are the differentials between RWD and AWD the same? Also would anyone know where I could find the seals bearings and washers required for this swap?

I have access to all the tools required for this, so that's not the issue here. Thanks in advance!

LSD
http://www.teammfactory.com/helical-lsd_165
 

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Before I spend the time educating you about differentials, may I ask why you would want to go through the trouble of retrofitting LDS(s) into your xi? For all the drifting you'll be doing?
 

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Discussion Starter #5
In short that really is the main point^^^. in snow more than anything. I'm sure it also can add slight track advantages as well. Mostly I need a project for my drive train class so why not this?
 

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http://www.bokchoys.com/differential/GearRatios.htm

Here's a full list of BMW gear ratios. e46 xi's have four options: 3.07 (330xi manual), 3.23 (325xi manual), 3.38 (330xi auto), and 3.46 (325xi auto). e83 X3 diffs have also been reported to work. I could write you a novel about diffs and ratios and highway rpms and DSC and understeer and why LSDs on an xi are pointless, but I'll just wait for more specific questions.

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Discussion Starter #11
http://www.bokchoys.com/differential/GearRatios.htm

Here's a full list of BMW gear ratios. e46 xi's have four options: 3.07 (330xi manual), 3.23 (325xi manual), 3.38 (330xi auto), and 3.46 (325xi auto). e83 X3 diffs have also been reported to work. I could write you a novel about diffs and ratios and highway rpms and DSC and understeer and why LSDs on an xi are pointless, but I'll just wait for more specific questions.

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That's an actually very interesting list=) It's a shame they never put lower gears in the XI's. They could definitely use a little more low end oomph imo. I understand the basics of drive train function fairly well, though I'm not entirely familiar with the deep workings of the X-Drive . However if you believe this would be a poor decision/investment I would actually be really appreciative if you could expound on why you think this is something I wouldn't want to do. It's a rather large sum of cash to pull this off and I'd rather not do it for little to no gain=P

I value your time and don't want to waste it for something trivial if possible. Maybe you could steer me towards some articles, so I could better understand the subject?

Thanks!
 

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This forum and others like it are really the best places for information on the subject. I trust you know how to Google; it's amazing what you can deduce by comparing a few analogous threads. The website I linked you to earlier has a bunch of good numbers and a great gear ratio calculator with presets for different e46's (I'll get to that in a bit). xiftw.com is also a good resource.

A few basics... The e46 4WD system starts at the tail end of the transmission with a gear driven transfer case that provides a constant 38/62 front-to-rear torque split. X-drive wasn't introduced until the e90 generation, which added a motor to the transfer case to vary the torque split. The e46 xi's rear end is comparable to RWD cars. The front differential is a smaller unit bolted to the driver's side of the engine, with one half-shaft passing through the oil pan. Both diffs are open, as you know, but DSC does provide a degree of simulated lock by manipulating the brakes. DSC works great in the snow, terrible on the track, and cannot be completely disabled in xi's.

As to why you shouldn't bother with LSDs, there are many factors. Both diffs would have to be custom jobs. These cars were never meant to be tracked, and adding a front LSD would only magnify the existing understeer. The chassis, suspension, and power delivery is just nothing like the e46's sport-oriented AWD rivals. This drivetrain was designed to comfortably add a bit of front axle participation on an icy street, not smoke all four tires around an apex. Adding a locking rear diff is a bit more realistic, but even then the cost-to-benefit ratio would be astronomical, you'd need an s54 or supercharger to justify it, and DSC would kill your fun on the track anyway. We're getting into some crazy **** for a decade-old 4WD luxury sedan, and while somebody out there will inevitably try it, I assume you're not that somebody. For the track, you should have bought a ZHP.

With that said, a ratio swap with open diffs from another model would make for a practical, pronounced upgrade on the street. My manual would benefit nicely from a set of 3.46's. With your automatic, you may need to start researching e83 diffs for any significant boost. Keep in mind, however, that the shorter you go, the higher your cruising RPM will be in top gear, which can get uncomfortable and kill gas mileage. Use the calculator I mentioned before to keep yourself from going overboard.

I hope this points you in the right direction. As far as your drivetrain class project goes, a diff swap is a diff swap, LSD or not...
 

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^ Well written with supporting statements. Now how about a super-charger class project? Same bucks more kick!
 

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We will see about that!




Had an m5e39 rear axle and 330xi front axle on last car, worked great!


Next friday im taking my 800hp 330xi to Mantorp track here in sweden!

Full rollcage, k-sport super racing suspension, fully built engine!
 

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A built car like that certainly necessitates an LSD. I was speaking more from the standpoint of a relatively stock daily driver. Im curious, was the M5 diff a direct bolt-on or did it require the loaded rear subframe and custom driveshaft like an M3 swap?
 

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Discussion Starter #18
Yes thank you! Very Insightful! I was actually under the impression that my car had transferable torque. But frankly I prefer the constant split distribution. I have a Volvo that has variable torque and I really don't like intervening with my driving all the time=( I've been very happy with the XI's handling, and the AWD is a must for my area. So I just liked the Idea of adding a posi to reduce the intervention of the traction control, making the car feel a little more RWDish in the corners(Hoping more for the Audi style handling without the craptacularly expensive maintinence). EX of desired handeling: https://www.youtube.com/watch?v=H1C1JigN8zw
But logistically upgrading tires and suspension may have a more desirable affect on traction than an LSD would. It also appears that the LSD I was looking at is for manual only cars, so I don't think that would fly too well=( Sigh..

Thank you for helping me to revise my plans, I see now that there are better ways to spend my money. Like you said, if I get more power at the wheels this may become necessary. Hopefully a supercharger, an ls7, or both is in the works. Though I don't know of anyone who has tried an LS in the XI. And I don't really want to pull my car apart only to find that it doesn't lol. Sounds like a topic for another time I guess...
 

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Discussion Starter #19
We will see about that!



Had an m5e39 rear axle and 330xi front axle on last car, worked great!


Next friday im taking my 800hp 330xi to Mantorp track here in sweden!

Full rollcage, k-sport super racing suspension, fully built engine!
Holly s*** that's awesome! Please please please post a video when you do!
 

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I have a question a bit off-topic.

I have a 325xi Touring and was wondering if the diffs, transfer case and tranny are the same as a 330xi sedan. The 325 feel a bit under power... I am considering a 330 engine swap to keep the xi otherwise I will buy a salvage E46 M3 and will swap everything next spring.

Also, it is possible to swap the 6 speed tranny from a 330xi into my 325xi and keep my diffs and transfer case?
 
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