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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 04-25-2017, 08:14 PM   #1
Manchicle
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$200 rwd conversion

I've been working on a little side project and I've finally made enough progress to post about it here. I picked up a junkyard transfer case and welded up the planetary gearset inside. Not the prettiest welds, but there are more than enough throughout, and the final re-sealed diff spun smooth as new. With a locked center diff, I can run without a front driveshaft and enjoy the RWD. I swapped it in this afternoon and had a very successful ride home. No noise or vibrations way beyond highway cruising speed plus all the perks of rwd (noticeable power bump, oversteer under throttle, slip when I wanted it). DSC wasn't too happy with me when I did mess around, even with it "disabled", but I risked a few clutch dumps in the rain and got plenty of standing wheelspin. I'm going to unplug the unit soon and see what it can really do. The plan for now is to leave the front diff and axles in, the idea being to swap the old transfer case back when I put my snow tires on. But you never know...




Last edited by Manchicle; 04-25-2017 at 08:18 PM.
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Old 04-27-2017, 02:18 PM   #2
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Why?
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Old 04-27-2017, 03:00 PM   #3
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Why?
I mean, I could give you a dozen reasons. Do I really need to go thru why someone might want to go rwd, especially from our mediocre 4wd system? Theres a thread on here asking about it like once a month.

And to those of you who wanna say "shouldnt have bought an xi" or "go buy something else", its not nearly that simple. For one, I was sort of rushed into buying, and this xi was the best I could find at the time. This is my one and only car, my DD, and I dont have the cash or parking space available for another project car. I very much appreciate the 4wd when it snows, but 95% of the year I'd prefer rwd. I live to **** around with it and I've exhausted most of the common, "affordable" mods. So for $200, I was able to completely transform the way the car drives, and its easily reversible in about an hour one night at the shop (unlike a full tranny swap). And as far as I can tell its never been attempted before, so theres a pride factor there too in formulating a mod that works out in the end. How many e46s do you know of that get the best of both worlds?

Just putting it out there to those who want to know if its possible. I figured I might get at least one or two "cool man, good to know" responses. But I guess I'm crazy...
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Old 04-27-2017, 03:27 PM   #4
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Originally Posted by Manchicle View Post
I mean, I could give you a dozen reasons....
Please do.
Quote:
Originally Posted by Manchicle View Post
Do I really need to go thru why someone might want to go rwd, especially from our mediocre 4wd system?....
Yes. Spend particular time on our 'mediocre' all wheel drive system.
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There's a thread on here asking about it like once a month.
No, there's not. And even if there was, the answer would still be the same.

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But I guess I'm crazy...
I would tend to agree...
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Old 04-27-2017, 04:35 PM   #5
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Please do.
Yes. Spend particular time on our 'mediocre' all wheel drive system.
No, there's not. And even if there was, the answer would still be the same.


I would tend to agree...
Lol jesus christ man. I LIKE MY CAR SO YOUR MOD IS OBVIOUSLY WRONG! Guess I'm glad to be leaving the xi crowd...

- more power to the ground (by far the biggest butt-dyno bump of any of my mods)
- far better chassis dynamics (I can actually throttle-on oversteer now)
- smoother ride without front axles being driven by the engine
- bump in gas mileage
- weight savings (especially if I drop the front diff and axles)
- launches
- burnouts
- the simple satisfaction of having designed and successfully completed a mod. Its what I enjoy.

And of course I could come up with more if I put my mind to it. I've been wanting to autocross the car, but I wouldn't do it with 4wd. Does it make any more sense to you now? Or is everything I listed above clearly bullshit?

I would really love to hear you explain how our 4wd system *isn't* as pedestrian as they come. 3 open diffs, no variable torque split, and an overly sensitive DSC system that you can't fully disable. Like, it obviously works fine enough in practice. I'll be the first one to tell you that xi's perform immeasurably better than an equivalent rwd e46 in the snow. I remember defending that position in a previous thread. Like I said, I'll be going back and forth. But on dry roads, our 4wd is absolutely nothing but a detriment compared to the alternative. Take the opposite of everything I listed above and apply it to xi's. Thats not to say that the 4wd option isnt worth it to many people, but I'm certainly not the only one around here who can see the merits of rwd. And as someone who pretty much lives in a shop, whats another hour of tinkering on top of swapping my snow tires every other season? No biggie.
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Old 04-27-2017, 06:34 PM   #6
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Lmao I though it was the rwd-or-bust infiltrators who were the snobs in this forum, but I guess it goes both ways. I was hoping for some reasonable conversation about getting the best out of our cars (which still very much involves and utilizes the 4wd system, exclusive to xi's). If theres a mod out there, maybe this thread belongs somewhere in the tuning section?

You're damn right I enjoy smoking my tires for fun every once in a while. And I know some of you would too
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Old 04-27-2017, 07:41 PM   #7
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I don't own an xi, but damn I wish I could seasonally switch between awd and rwd. Nice job. For $200, sounds like a pretty good deal, even if some labour is involved. Next project, find a way to switch it on the fly.
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Old 04-28-2017, 09:11 AM   #8
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I don't own an xi, but damn I wish I could seasonally switch between awd and rwd. Nice job. For $200, sounds like a pretty good deal, even if some labour is involved. Next project, find a way to switch it on the fly.
Thanks. I know not everyone around here does their own work, but for those who do...

And yeah, thats taking it to a whole new level. No engineering degree here haha
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Old 04-28-2017, 09:52 AM   #9
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I'm missing the point as well. If you want a RWD car, it seems like you should buy one. Or convert the XI to rwd with the proper parts, or changing the dif instead.

Um, cool test I suppose. You did the same thing cheap drifters do with an open dif.


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Old 04-28-2017, 10:33 AM   #10
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I'm missing the point as well. If you want a RWD car, it seems like you should buy one. Or convert the XI to rwd with the proper parts, or changing the dif instead.

Um, cool test I suppose. You did the same thing cheap drifters do with an open dif.


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Well part of the point is that I do want to be able to go back to 4wd for the winter, and I already went thru the "buy another car" thing, its just not realistic. It was between a full tranny swap or this transfer case experiment, and with cost, ease of installation, and storage of my spare parts factored in, the transfer case was the way I went.

And yeah, I welded my center diff essentially the same way people have been welding their rear diffs forever. Only I did it so that I could run with only one output shaft...
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Old 04-28-2017, 11:06 AM   #11
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Thank you for sharing this mod.

How much time will it take you to convert back to AWD for winter?
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Old 04-28-2017, 11:51 AM   #12
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Thank you for sharing this mod.

How much time will it take you to convert back to AWD for winter?
Happy to share. Its really just a straight transfer case swap to go back. I pulled my car in just after 5pm on tuesday to do the swap and was on my ride home before 7. I'm a professional with a full tool set and a lift though, so I imagine it would take maybe 2-4 hours in someone's driveway
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Old 05-01-2017, 08:22 AM   #13
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damn, Ive seen some posts of people doing these transfer case welds to do the rwd conversion but I never end up getting feedback of how it ends up working out after a while. I know the rear diff can withstand all the power to the rear because its the same diff as the rwd, but idk about the transfer case. How many miles have you had your xi rwd?

My front diff just exploded and I am considering picking up a used, cheap transfer case and following in your steps with the rwd conv. until I find the right ratio front diff to slap back in.

Sucks that people have to **** on mods and creativity like this, like how many of your lug nuts have to be torqued to spec for you to be that much of a dick?


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Old 05-01-2017, 08:58 AM   #14
Manchicle
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damn, Ive seen some posts of people doing these transfer case welds to do the rwd conversion but I never end up getting feedback of how it ends up working out after a while. I know the rear diff can withstand all the power to the rear because its the same diff as the rwd, but idk about the transfer case. How many miles have you had your xi rwd?

My front diff just exploded and I am considering picking up a used, cheap transfer case and following in your steps with the rwd conv. until I find the right ratio front diff to slap back in.

Sucks that people have to **** on mods and creativity like this, like how many of your lug nuts have to be torqued to spec for you to be that much of a dick?


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Right? Some people...

Happy to be of whatever help I can. I've got all sorts of insight for you, way too much to just start throwing out there. You can PM me with questions, or just post em here for everyone to see...

I just passed 132k. I didnt have any 4wd related issues, just did it for fun. I did take the opportunity to replace the transfer case mount, guibo, and driveshaft support bearing, and all that new rubber definitely tightened up the drivetrain.

The transfer case can definitely take the torque. Same components used in V8 X5s as well as some big GM trucks.
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Old 05-01-2017, 01:22 PM   #15
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It looks like the planetary gears are welded on that ring gear, but could you verify what is welded to what? Really appreciate the info!


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Old 05-01-2017, 01:55 PM   #16
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It looks like the planetary gears are welded on that ring gear, but could you verify what is welded to what? Really appreciate the info!


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Sure. Let me sit down tonight and I'll give you a a good walkthru of how I went about welding
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Old 05-01-2017, 07:44 PM   #17
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Where to begin...

I'll touch on what I think is a pretty crucial step here at the beginning. Once you get the thing apart, you'll find a washer that normally floats between the planetary gear and the ring gear. It would appear that this washer must to be centered on the planetary carrier in order for the input shaft to fully seat when going back together. This washer is going to be exposed to a lot of heat, possibly even actual weld, and you do not want to risk it being off-center. I super glued mine in place using the input splines themselves as a guide (green in the pic below). Otherwise, you may never get the case back together.

So my initial plan was to do all of the welding on the planetary gear itself, out of the case. Once I saw how tight the tolerances were between gears, I felt more comfortable welding with the planetary gear sitting splined in position in the ring gear. And at that point you might as well just weld it all together, using as much surface and material as you can. Doing it this way significantly limited the access with my MIG welder (stick would probably be best), but I was concerned about heat distortion and wanted to be sure it would all fit back together. I even removed the inner sun gear from the other side of the case and inserted it into the planetary after every few welds to make sure it still fell in smoothly.

I did attempt to take the ring gear out of the case. I removed the rear output flange, seal, and snap ring, but it still didn't want to budge. I didn't want to mess with the bearing, so I decided to leave it in and weld right in the case. In retrospect, I'm sort of glad I had that seal out with a replacement handy, considering how hot the case got during the welding. Not sure how the seal would have held up. But on the flip side, installation of the seal and flange took some BMW specific tools that may not be so easy to replicate outside of a dealer, so I'm not sure what to recommend there...

A spare brake rotor makes for a great transfer case welding stand.

My first three tacks were right on the planetary gears where the teeth mesh into the ring gear (yellow in pic). I did these with the sun gear splined in place. Once I felt confident it was centered and not going anywhere, I took the sun gear out and went to work throughout the carrier (red in pic). First, I went down through the six elongated holes in the carrier and welded to the back face of the ring. I filled the vertical gaps between the planetary gears and the carrier, staying shallow so as not to interfere with the sun gear. I went to town in the large open spaces between planetary gears. And if all that wasn't enough, I made three complete passes filling the gap around the perimeter of the carrier/ring, making some really good penetration (blue in pic). Only problem there was I could only weld an inch at a time before needing to turn the unit for torch access.

And that was that. I smacked the thing around and did my best to get rid of all the spatter. Greased up the needle bearings, cleaned up the sealing surfaces, laid down a bead of RTV, and slapped her back together. Torqued the case bolts to 30 Nm (felt snug) and let it dry overnight. Installed my new seal and flange, topped her off with some fresh LT2, and threw her in.

Hope this helps


Last edited by Manchicle; 05-01-2017 at 10:26 PM.
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Old 05-01-2017, 08:47 PM   #18
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Wow, thanks for the details.

Did you convert the front end with RWD suspension/arms or just left it as-is without the CVs.
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Old 05-01-2017, 08:57 PM   #19
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Really appreciate the walkthrough! Really insightful, going to attemp this first on my old transfer case, and if all goes well, I have another used one in good condition that will be dedicated to this swap!

Apparently you need, at least, the axle flanges that go into the front hubs to secure the wheel bearing to the hub, and so you can get readings on your speed sensors. Just what I've heard


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Old 05-01-2017, 09:05 PM   #20
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Wow, thanks for the details.

Did you convert the front end with RWD suspension/arms or just left it as-is without the CVs.

No, the front end is all still completely together, diff and axles and all. At least for this first season, I want the ability to go back. If I get comfortable with it, I may remove the diff and axles for weight and drag savings. I wont be doing a full conversion. I've invested in too many fresh xi suspension parts to justify a swap. I understand I won't have quite the same geometry or travel as a factory rwd car. Not a concern.

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Really appreciate the walkthrough! Really insightful, going to attemp this first on my old transfer case, and if all goes well, I have another used one in good condition that will be dedicated to this swap!

Apparently you need, at least, the axle flanges that go into the front hubs to secure the wheel bearing to the hub, and so you can get readings on your speed sensors. Just what I've heard
Yup, you're totally right. I hadn't even considered the sensor aspect, but I knew I couldn't leave those bearings unsupported. Are you getting this info from other related threads? I couldn't find anything like this when I looked around...

Edit - now I realize I've just been looking for transfer case welding threads. Didnt really consider the overlap with the true rwd conversion.

Last edited by Manchicle; 05-01-2017 at 09:31 PM.
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