[gtaccord]

While it would be cool to be able to go rwd on a whim the system as it stands is not so bad. It is a rear drive biased system with a max 50:50 power dustribution. It is simple and fairly easy to work on and maintain when compared to more complex center diff systems.

The only real interest I have in disengaging the system would be the fuel economy benefits during the summer months but this could only be achieved thru locking/unlocking hubs (like 4x4 trucks) and would require a major hub/axle redesign.

[Windycitybimmers]

Does anyone know what fuse it would be on a 2006 330xi E90 im dying to do this!

[peter91118]

I have been getting a lot of PM's from people asking if my car is still fine with no front drive shaft. Ive done approximately 6k miles and still have no issues to report.

[stashtrey]

Originally Posted by peter91118

I have been getting a lot of PM's from people asking if my car is still fine with no front drive shaft. Ive done approximately 6k miles and still have no issues to report.

That is nuts. So do you feel like you're losing any power? I'm very curious about this.

Also..how difficult is it to remove the shaft?

Thanks for the update. Given mg situation with some annoying noise from my front end (not bearings...already replaced) this seems like a great way to isolate the noise and perhaps just leave it off. I don't need awd. I live in Sacramento lol.

[v1nc86]

Originally Posted by stashtrey

I don't need awd. I live in Sacramento lol.

so why did you buy a x-drive?

[tboudre]

Originally Posted by v1nc86

so why did you buy a x-drive?

Don't know about Mr. Sacramento, but an xDrive was purchased in Pennsylvania, owner moved to Florida, and it ended up in Louisiana where I got a great deal. Wasn't too excited about the AWD until it rained for 2 weeks straight and I learned I could take off on wet road as well as dry pavement.

Here's some enlightenment from wiki:
http://en.m.wikipedia.org/wiki/BMW_xDrive

It's all in the program and definitely possible. Is very intertwined with DSC.

[stashtrey]

Originally Posted by v1nc86

so why did you buy a x-drive?

I live 1.5 hours from Tahoe. I like awd most of the time but after 20k miles I'm interested in a change.

Why do you care?

[tboudre]

Originally Posted by peter91118

I have been getting a lot of PM's from people asking if my car is still fine with no front drive shaft. Ive done approximately 6k miles and still have no issues to report.

So from what I read on Wiki, it would seem that within 1/10 second, your ECU/TCU (not sure which) determines that there is no load on the front wheels, and transfers 100% load to the rear.

One other method would be to intercept the signal from the ECU/TCU to the servo that distributes the load. Has anyone tried this? It may mess with the traction control, but if you haven't had any problems with traction control disconnecting drive shafts... ???

[peter91118]

Originally Posted by tboudre

So from what I read on Wiki, it would seem that within 1/10 second, your ECU/TCU (not sure which) determines that there is no load on the front wheels, and transfers 100% load to the rear.

One other method would be to intercept the signal from the ECU/TCU to the servo that distributes the load. Has anyone tried this? It may mess with the traction control, but if you haven't had any problems with traction control disconnecting drive shafts... ???

Traction control is still not happy after excessive wheel spin. You can get a way with a little though. As others have said, everything is too interconnected. Software is the only safe way to do this.

As for not safe ways, i wonder if you pulled the front driveshaft as well as unplug all 4 abs sensors from the wheels would do the trick? This is assuming the ecu has no other way to tell about wheel speed other than the abs sensors.

[peter91118]

Originally Posted by peter91118

Traction control is still not happy after excessive wheel spin. You can get a way with a little though. As others have said, everything is too interconnected. Software is the only safe way to do this.

As for not safe ways, i wonder if you pulled the front driveshaft as well as unplug all 4 abs sensors from the wheels would do the trick? This is assuming the ecu has no other way to tell about wheel speed other than the abs sensors.

This is probably a terrible idea by the way..

[tboudre]

Originally Posted by v1nc86

so why did you buy a x-drive?

This reminds me of going into Radio Shack and asking for, uh, I dunno, maybe a 24 VDC power supply. They don't have it, should be end of story, but then they ask, "So, what do you want to do with it?" Why do you care? I want the power supply and you don't have it.

[tboudre]

I was talking to someone over here and came up with a brilliant idea! For those who want RWD to be able to dyno on a single dyno, all you should have to do is get the front wheels off the ground and the power should be fully transferred to the rear, and voila! Admittedly, I've never put my car on a dyno, so... would this be dangerous? Could it be done safely?

[v1nc86]

Originally Posted by tboudre

This reminds me of going into Radio Shack and asking for, uh, I dunno, maybe a 24 VDC power supply. They don't have it, should be end of story, but then they ask, "So, what do you want to do with it?" Why do you care? I want the power supply and you don't have it.

I asked because I don't see why an awd car can help you in South Cal. I do have an x-drive, but I live in Montreal where summer gets hot 30+ Celsius (90+ F) but we also have a long 6 months winter where we get -30 Celsius (-22 F) so any awd car is very useful. With that said, you can buy whatever you want...

[stashtrey]

Originally Posted by v1nc86

I asked because I don't see why an awd car can help you in South Cal. I do have an x-drive, but I live in Montreal where summer gets hot 30+ Celsius (90+ F) but we also have a long 6 months winter where we get -30 Celsius (-22 F) so any awd car is very useful. With that said, you can buy whatever you want...

I live in northern CA not southern. I am less than 2 hours from Tahoe and the Sierras. But yeah.. we can all buy what we like.

Also... I like to tinker. Most in here do.

And...acceleration in an xi is amazing and fun. Why not, as many have mentioned in this thread, explore the best of both worlds.

[tboudre]

I sat down and read the WHOLE thread! What ever happened to this guy? It sounded like he was on to something, but then disappeared off the face of the forum.

Originally Posted by blauner335

Sorry for the delay. I have been really busy lately. Just moved into a new house a couple weeks ago so that has been taking up lots of time. Anyways, I looked around some on the car and have been looking things up on the system. I've learned a lot, but there is still a lot more I need to know. The servo control motor was a little different than I thought it was going to be. Not a huge problem though. I am refining my idea a little bit but I think it will turn out much better. I think this is going to turn into a summer project for me. I am going to need to take a lot of data with the car up and running to make sure I get this right.

I haven't had any game changers yet that says you cant do this, but like I said before, I don't want to get everyone's hopes up so don't take this to the bank.

Originally Posted by blauner335

Update on my status:
I am taking tons of data at the moment and trying to reverse engineer some things. I can see the light at the end of the tunnel. This is really getting fun

[tboudre]

But anyway... In all the pages and pages, has no one ever found the transfer case controller under the passenger front floor mat? I thought about disconnecting the servo motor, but without a lift, it was going to be difficult to plug & unplug. Through some online parts lists I found the location of the transfer case module, and some information on it. Through some experimentation I found that unplug the farthest right plug on the module (closest to passenger door) and you get the whole array of Christmas tree lights, probably similar to pulling the fuse, but only powering down this module. I think this module takes CANBUS commands and moves the servo accordingly. I think unplugging this connector disconnects the module from the CANBUS. I drove around a bit like this and I was spinning the back tires like crazy. I plugged that one back in and unplugged the connector on the left, closest to the driver's door. This one only gave me AWD malfunction, and the triangle circle as if DSC was disabled, but did not say that DSC was disabled. I went for a ride again, and there was rear wheel spin, but not as much. I tried pressing the DTC button, but it was unresponsive. I was on dry pavement, so it was hard to tell what was going on, I still seemed to have plenty of traction. Maybe with AWD malfunction computer does not let you override DTC? Error did not clear when I reconnected the connector. I let the computer go to sleep (10+ min with remote 30+ ft away), then started and traction light was cleared.

[stashtrey]

Originally Posted by tboudre

I sat down and read the WHOLE thread! What ever happened to this guy? It sounded like he was on to something, but then disappeared off the face of the forum.

Looks like he went to o the dark side!

http://m.audiforums.com/forum/showthread.php?t=207992&styleid=6

[RallyRcrr]

SOLVED...maybe!!! Possible repeatable solution found!!

Similar to Blacksails post about being rear wheel drive when the 4x4 error appears, I was able to take my 335XI to the Ridge Motorsports Park in Washington and did an entire afternoon track session in RWD only.

How?
It was quite by accident, but if you can enable the 4x4 warning and leave it on your AWD will be RWD until the warning is reset. If you have a Cobb AP this warning can be enabled at any time.

During a lunch time break at the track, I decided to change the tune on my 335XI with my Cobb AP. Unfortunately, I ran out of time when the call for the next run group to start came. The ECU rewrite completed, but I didn't power off and power on the car after the tune was complete, and impatiently rushed onto the track. The 4x4 warning error was still showing on my dash as I hit the track. As I started to do my laps, to my surprise the car felt completely different. The corners I could apply power on early were turned into corners I was starting to rotate the rear out. I had to back off because I was starting to drift due to throttle induced oversteer. I experimented and found I could do full drifts if I wanted. To make sure it wasn't just my imagination I went to the pits and did a slight burn out and confirmed from a by stander only my rear wheels were working.

Reliability
Can't speak to long term, but I haven't had any issues with the car. I ran the whole day with no problems. It's been a month since my run at the track and I've done this several times since.

At the beginning of my post I said this maybe a solution. I'm a sample size of one so I would appreciate some others give this a try and confirm that this is possible on other peoples cars. Let me know!!!

My steps:
1. Use Cobb AP to change tune (doesn't matter which one)
2. Wait for the Cobb to finish
3. Confirm tune is finished and 4x4 error is displayed on dash.
4. Don't shutoff the car, instead start it.
5. Car is now in RWD only mode until car is shut off.
** Car returns to normal AWD operation after powered off and restarted.

[ACM335xi]

wow this is a very interesting thread, I wonder how reliable this would be.

[tboudre]

Could you tell if traction control was on or off, and if on, could you turn it off with DTC button?

[Pseudo Nim]

Originally Posted by tboudre

Could you tell if traction control was on or off, and if on, could you turn it off with DTC button?

If I'm not mistaken, when the 4x4 warning is on, car is indeed RWD only and DTC is fully off (it's supposed to be an "emergency" mode).

[tomtom11]

THIS IS AWESOME NEWS!!! any way to do this with jb4?