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About a week ago, on my way into work, I ended up running over a huge chuck of concrete at about 40 mph. Since my car is only about 4 inches off the ground, my oil pan lost the argument. With no dash lights and no visible stream of oil in the rearview mirror, I nevertheless thought it a good idea to pull over and inspect for sanity sake. I was stopped for about 30 seconds by the time I got to the front of the car and looked under when I saw the 18 inch diameter puddle of oil. I quickly shut off the car, said a few bad words, then set about getting it back home.
Over the course of the next few hours incoherent thoughts began to focus in on a thought that was really more of an idle comment when I first bought the car - I wish it was 2WD.
I'd always dismissed that as a pipe dream but then I started looking into what it would actually take. As it turns out, not really that much. To be accurate, not really much *more* that to just replace the stock oil pan. Just to get to the pan, one has to essentially remove the entire underside of the front of the car - half shafts, differential, subframe, steering rack, and spindles (kinda anyway), and probably a few more things I haven't found out yet. With a 2WD, you put a new pan on then subframe, spindles, Bob's your uncle, you're done! With AWD, many things have to be done.
I'm of course leaving out a lot but I guess that's the point of this thread - so with that, check back from time to time to see how things progress in making my car into a quasi garden variety, pick up on any street corner in Europe, 2WD handshaking wagon. Or, as it's been dubbed - Unicorn Ohne Allrad.
Been a bit dark on the update front, I've been spending most of my time trying to make progress!
Anyhoo - a few pics of the damage. As you can see, it was a significant punt (as if the cracked oil pan wasn't indication enough):
As I mentioned before, I'm making this a 2WD wagon "while I'm in there" mostly because I can. I'm an engineer at an engine company and I'm baffled with the looks and questions I get when I try to explain to coworkers why I'm making the change - chief among them is "why do you want LESS traction?" I try to explain that 2WD with snow tires >> AWD with all-seasons but it falls on deaf ears. Apparently AWD marketing has worked.
I decided to go full conversion since it just seems like the right thing to do and parts are fairly inexpensive. To be honest, I'm pretty interested to see the weight savings as well. The 2WD subframe is aluminum against the steel AWD subframe, never mind the savings from removing all the AWD bits. As well, from a maintenance perspective I've cursed that steel subframe many times. I'm not expecting open access with the alu version but it is not nearly as bulky and in the way.
Back on task. I've been doing a lot of research, scouring the internet/ebay/junk yards, amassing parts, and generally laying out a plan of attack. Once I got the parts needed early in the process I dug in.
Most everything removed:
Without a lift, the steel AWD subframe (~48 lbs) was a little rough to balance while I got out from underneath it but I managed. Without the transmission, transfer case, or front drive shaft I'm at minus 100 lbs, which is pretty exciting. Hoping for about 200 lbs when it's all said and done.
<--- AWD pan 2WD pan -->
Pretty intricate casting if you ask me. Also, minor error on my part to assume that since both pans are rear sump the oil pick up is the same. This is not the case and I'm waiting on a 2WD pan oil pickup to arrive.
I've got other things to do while I'm waiting, like put a bigger rear sway bar on it. With the 2WD subframe, I had to replace the front bar anyway so I decided the rear was needed as well.
Research showed the front xiT bar is 25.2mm vs 26.5 of the M5. Not a huge change because I didn't feel like the Euro M5T (28mm) or M6 (29mm) were merited. Out back the stock rear xiT bar is 12mm vs 18 of the M5 sedan. The Euro M5T, plus the M6 gets a 20mm bar but I opted against that thinking the 18 should be enough to tighten things up without making uneven bumps unbearable or tank slappers inevitable.
M5 sedan vs xiT rear bars:
I also got the ABS pump swapped out, but there's nothing to see really. They look the same. I have ZERO desire to relocate the pump to behind the fender liner, M5 style.
More to come, thanks for reading!
For slightly more regular updates, I try to post on Instagram (@the_mexler) when I make decent progress on any given day
Andy
07 530xiT 6MT, soon to be de-exed
Last edited by amesser325; 12-07-2017 at 06:20 PM.
Reason: added Instagram call out
Significant progress yesterday - got the pan, subframe, and steering rack installed. Hit a few snags along the way, though... the strut diameter is *smaller* on the xdrive front end, and the steering cluster is completely different between 2 and AWD all the way back to the steering wheel.
Since I installed the ISC coilover kit I was planning on just swapping in the 2WD spindle (backed up by a call to ISC that they would drop in, but we must have crossed wires since the two are about 6mm different in diameter). I think this can be remedied by a new lower sleeve on the coil over, need to call them again.
The steering cluster looks to be a direct take-off from a 530i sedan, but as I've found out you won't know until you go to bolt everything together. Yet another trip to the bone yard I guess... such is life.
Definitely a different oil pickup tube:
I'm pretty meticulous about torque + angle bolts - the middle 2 have torque + 90 degrees, outer 2 have just torque:
Hoepfully I'll have the old tranny/transfer case popped out and new installed today so I can start the rear mount fabrication.
With the progress over the weekend I was able to dig into pulling the transfer case and transmission, and because I've been needlessly focused on weight savings, I immediately weighed the rest of the bits. Total savings came in at 195 lbs, just a tick under my hope/projection of 200. Pretty solid. I think the impact to drive line resistance will be more significant to fuel savings but 200 lbs is still 200 lbs.
Upon further study, I'm now most interested in knowing the impact of the changes to the steering geometry. When I first started out, I assumed the part number difference was more a reflection of the increased effort to steer an AWD front end (and thus just an overboosted 2WD rack) but it goes a lot deeper. specifically, the steering column adds a bearing at the firewall as well as an additional u-joint between the rack and the firewall bearing. Turns out this is to clear the left side half shaft. This forces the AWD rack input shaft angle (from horizontal) to increase to ~50 degrees from the 2WDs ~30 degrees. I don't think that itself increases effort but it impacts the rack location from the axle and steering axis and also adds the complexities noted in the column - the more joints, the more effort. Once I lowered my car, I felt the steering effort got a bit too much. I'm not opposed to heavy steering, but this just seemed too heavy. It's understandable given the geometry changes to the tie rod/spindle interface. I'm quite interested to see if the feel is similar with the 2WD front end and presumably 'better' steering setup.
A few noted oddities comparing the AWD/2WD parts. I would have thought the loading, in general, of the AWD system would drive everything to upsize, however:
1) The 2WD strut is ~5mm larger diameter (57 vs 62mm)
2) The 2WD control arm bushings are ~20mm wider for both CA and tension struts
Anyway, waiting on a few key bits to close out the subsections, like strut end caps, odd bolt sizes (120mm control arm bushing bolts!!), small heat shields, etc but I can start to see the light at the end of the tunnel.
A bit of a slow down as I'm waiting on a few small bits to close out the front suspension work. Really small - power steering o-ring to seal the supply line from the pump... But also big - still working on getting the new strut lower end cap to fit the 2WD spindle.
With a few extra hours to kill I decided to start on the electronic side. I modified the VO to remove the VTG business as well as change the chassis code to a euro 2WD wagon, which seems to have taken but I can't seem to make the VIN change on the DSC module I swapped in to remove the DSC-X stuff.
Can anyone confirm the proper *.prg for a 2WD DSC module is DSC_60.prg? That comes up and it seems to read the module but when I try to write the VIN to it I get an error. I'm not exactly a power coder, but I did swap out to an LM2 a few years back. Revisited those guides plus a bunch of searches but nothing specific to what I'm doing.
More hardware due to show tomorrow, namely the rear trans support, so I can get back into the mechanical realm and show myself some progress!
I was ale to make some decent progress tonight. After several strike outs at local hose shops and a few tuner retailers, I decided to have a custom clutch slave cylinder hose made that got rid of not only the CDV but also the [presumably] cooling loops just before the slave cylinder. I recognize I'm taking a small risk but after about 5 different clutch bleed attempts using 2-3 different methods (plus a local independent not really being able to get it quite right), I decided there was no better time.
These loops are why I think it's a bear to bleed this clutch:
Unfortunately this required removing the master to slave cylinder line from inside the car, which in itself wasn't a big deal but in order to get to said line it required removing the carpet as the line runs under the carpet to the transmission tunnel. Rather than remove the entire dash to take the carpet out in one piece I opted to cut it just under the console so it will stay in the right position while still being able to come out. Once I got there everything was easy.
The shop brazed on traditional fittings that allow for easy assembly.I had been waiting for the hose modification before installing the transmission so I could more easily pass the highly shaped hose through the tunnel without being restricted by the bell housing (this was very helpful).
Beyond that work, I got the transmission fully installed so that now rear mount fabrication can begin. I can hopefully get that done before week's end but time may be the big issue for me. I also got the power steering system fully buttoned up so I can add fluid and check for leaks. While waiting for the coil over lowers, that will surely be the pacing item for the entire project, I think I'm going to come up with a way to hold the spindles in a semi-ride height location so I can install rotors and calipers without leaving everything hang and overload the ball joints. This will let me bleed the brakes and clutch, then it's just tranny and diff fluid, reinstall seats, drive shaft/exhaust.
And the coil overs...
Finally got some QT with my welder to fabricate the rear trans mount. I tried to do as much as possible off the car, as it always makes me nervous welding on a car, lest I fry a module. Alas, disconnect battery negative and keep the ground path as short as possible and tack in place, then remove for full welds.
The end result turned out OK. I probably should have gone with a larger hole and tubes inside the frame mounts, as the bolt holes needed a little persuasion to get all 6 lined up and bolts threaded. I decided to go with a rivnut drilled into the chassis on the left side of the car towards the engine in order to have the transmission/engine load reasonably balanced side to side and front to back, rather than cantilever to pick up the existing 3 holes all behind the tail of the transmission. I don't have access to a machine shop so I ended up using a bench vise to bend the wings that grab the rubber mounts. Not ideal, but should be fine since it will cradle the thing (not drop it in case of lost nut!).
You can see the cross hair where I drilled and installed the front rivnut. Just used 2 of the rear 3 holes.
Also found the solution to my suspension connundrum - It makes sense, really... just use a shim between the strut and the spindle.
Pretty simple solution and was getting close to having a local machine shop machine some out for me before I found these digging through KW installation manuals. Hopefully I can get to where it's ready to go on the ground in a few days. Just need to have the shifter parts arrive then I can button everything up and see if the ABS module reprogram was done correctly.
After the attempt at a less expensive shifter (used, from Europe) that failed I'm somewhat of a shifter guru. More importantly, I finally ordered the correct shifter parts and got the car on the ground.A quick test drive came up with a Servotronic error that was remedied by removing $S216 from the VO.
So now I'm off to the alignment shop tomorrow to finalize the last piece.
I'm toying around with the idea of a PDF write-up to document everything with options along the way - seems like some of the research I did along the way had several people looking to get rid of xDrive for a few different reasons. In any event, althought I didn't have too many surprises along the way hopefully it can be used to make it even easier for the next guy.
Also, I assume everyone saw the recent BaT auction for the 08 535xiT 6MT go for $22k? Sheesh, might need to think that one over!
Congrats and we are happy for your success, Captain Kirk!
When you get a chance, can you give me and a few of us some suggestions on how to lower the sub-frame. I have a 2006 530i and I think the oil pan has a slow leak with the gasket.
Thanks for sharing!
Originally Posted by amesser325
Great success!
After the attempt at a less expensive shifter (used, from Europe) that failed I'm somewhat of a shifter guru. More importantly, I finally ordered the correct shifter parts and got the car on the ground.A quick test drive came up with a Servotronic error that was remedied by removing $S216 from the VO.
So now I'm off to the alignment shop tomorrow to finalize the last piece.
I'm toying around with the idea of a PDF write-up to document everything with options along the way - seems like some of the research I did along the way had several people looking to get rid of xDrive for a few different reasons. In any event, althought I didn't have too many surprises along the way hopefully it can be used to make it even easier for the next guy.
Also, I assume everyone saw the recent BaT auction for the 08 535xiT 6MT go for $22k? Sheesh, might need to think that one over!
11-22-2017, 05:24 PM
Project Unicorn Ohne Allrad
