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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > All-Wheel-Drive (Xi / xDrive) Talk > Xdrive conversion to rwd



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      03-25-2018, 10:09 PM   #1
M_spiels
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Xdrive conversion to rwd

So I've been reading a whole bunch of different forums but no one has seem to ask the question. People say best way to go rwd is to remove the front driveshaft. I understand that just doing that makes it rwd and allows you to burn rubber and whatnot but thats not what im looking for. The awd system reduces power to the rear wheels by sending power to the front, my question is does it make more power to the rear wheels because you r essentially removing the power to the front wheel? Thanks in advance to anyone who can help me.
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      03-25-2018, 10:22 PM   #2
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It's just more parasitic losses. The engine needs to do more work to rotate all drive-line components leading to less power at the wheels.

Removing the front halfshafts would barely reduce the parasitic losses. The transfer case, front driveshaft, and diff take up more.

I'm not sure if you mean the actual drive shaft (haven't heard of anyone doing that), but I know people remove the halfshafts.

I think your best bet it to just sell it and buy a rwd if you really want rwd.
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      03-25-2018, 10:29 PM   #3
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Quote:
Originally Posted by Antetokounmpo View Post
It's just more parasitic losses. The engine needs to do more work to rotate all drive-line components leading to less power at the wheels.

Removing the front halfshafts would barely reduce the parasitic losses. The transfer case, front driveshaft, and diff take up more.

I'm not sure if you mean the actual drive shaft (haven't heard of anyone doing that), but I know people remove the halfshafts.
Im talking about taking out the shaft that connects the TC to the front diff its like 8 bolts 4 on each side that hold it on
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      03-25-2018, 10:40 PM   #4
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Quote:
Originally Posted by M_spiels View Post
Im talking about taking out the shaft that connects the TC to the front diff its like 8 bolts 4 on each side that hold it on
Ok that's the front driveshaft. Actually come to think of it I think people do actually pull that, not the halfshafts, it makes more sense.

Theoretically, you would put slightly more power to the wheels since you're only spinning a few more gears in the transfer case versus rwd. But we're only talking like 3-5% here, so like 8-13hp on a stock car, probably not noticeable. Not to mention still 300lbs heavier than the rwd version. And tougher to work on, and worse aftermarket parts.
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      03-25-2018, 10:48 PM   #5
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Quote:
Originally Posted by Antetokounmpo View Post
Quote:
Originally Posted by M_spiels View Post
Im talking about taking out the shaft that connects the TC to the front diff its like 8 bolts 4 on each side that hold it on
Ok that's the front driveshaft. Actually come to think of it I think people do actually pull that, not the halfshafts, it makes more sense.

Theoretically, you would put slightly more power to the wheels since you're only spinning a few more gears in the transfer case versus rwd. But we're only talking like 3-5% here, so like 8-13hp on a stock car, probably not noticeable. Not to mention still 300lbs heavier than the rwd version. And tougher to work on, and worse aftermarket parts.
I just had my car dyno'd made 293awhp which in my opinion is pretty low and 380ftlbs of tq i havent been able to find any dyno numbers of other n55 e92xi's but im fbo cp,dp,5" stepped fmic, bms intake, vrsf turbo outlet,strait piped, 2 step colder ngk plugs. So if i could turn tht 293 into something like say 320 rwhp by removing the driveshaft and also b able to have a little bit more fun I figured why not
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      04-11-2018, 12:33 AM   #6
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You’re going to have worse traction for little power gain IMO and a hit to resale. Just sell and buy a non-XI N54 if you want power without AWD lol.
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Last edited by dsjr2006; 04-11-2018 at 11:21 AM.
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      04-11-2018, 09:57 AM   #7
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Quote:
Originally Posted by motiv7891 View Post
Alternatively, you could simply unplug your transfer case motor. In theory with the driveshaft disconnected the car can still try to send power to the front wheels. Now it will probably notice that it's not doing anything, think the wheels are slipping and send the power to the back again, but its still throwing power back and forth. I don't think you'll gain anything there.
Now, if you unplug the transfer case motor, the car cant move the power around at all so its gonna be stuck in rwd mode. IMHO this is really the only option for people that want to "play" like that as disconnecting a driveshaft still allows the car to send power forward, even if it's not going to the ground...meh
You WILL throw codes and your dash...well it may begin to look a lot like Christmas.
So wat ur saying essentially is to disconnect the driveshaft along with unplugging the fuse 26 and 50 or watever the two fuses are?
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      04-11-2018, 11:21 AM   #8
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(Why this thread is in the N47 section is beyond me...)

You guys might be interested in checking out this ongoing thread.
http://f30.bimmerpost.com/forums/sho....php?t=1484545
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      06-22-2018, 01:35 PM   #9
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Quote:
Originally Posted by motiv7891 View Post
Resurrecting this one. I will have coding capability soon and will be testing the functionality of disabling the X-drive functions. Some things I am going to try to discern from this test.
Does the car like it? - does she operate as if it was never there, or are we throwing codes?
Does the car handle? - lets face it, it was set up as AWD, it MAY drive like crap with only the rear wheels pushing it.
Does DSC/DTC function properly? - or does it flip out left and right?
What happens in the rain/weather? is it suddenly a death trap...I have a 4-year-old so rest assured this one will get EXTRA consideration.
Is there any benefit???? Let us pretend everything checks out all safe and the car drives predictably...is this going to be worth the time and trouble?

What I want to do is perform this test to answer all of these questions and more. If this does SOMEHOW pan out, im in talks with some people to perhaps harness a way to control the xdrive function on older BMW's (think F90 like control...albeit not an M-tuned system..it would be slightly more utilitarian). For some time there has been a lot of debate. and the only tangible answers I can find are from people removing fuses or unplugging things. Far from a permanent solution and there is no way to test reliability when your wipers and turn signals won't shut off. With any luck, I will have some definitive answers shortly. Stay tuned.

P.S. Should you be inclined to remind me that I bought an AWD drive vehicle and I should "sell it and get a RWD" I swear to God there is no end to the hell I will deliver your way. I don't wanna hear it, this is to investigate the possibility of harnessing the power of xdrive for more than it was intended. Keep your pithy comments to yourselves. YOU KNOW WHO YOU ARE!
I much prefer the idea of being able to control the bias like the new M5 rather than completely disabling a couple hundred pound system that offers no functionality, but still adds weight.
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      06-22-2018, 01:45 PM   #10
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I like the premise of being able to select it's bias, but more useful might be the ability to tell the DSC how aggressive you want it to be with it's torque adjustments.

I'm thinking like the "terrain selection" in newer junk that goes offroad and doesn't have a real part time transfer case.

I'd very much like to be able to tell the DSC that I want it to be aggressive with the front torque because I'm driving in snow.
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      06-27-2018, 06:33 PM   #11
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Hmmmm...interesting.
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      07-11-2018, 12:12 PM   #12
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I had my E91 setup as RWD, just by pulling the connector on the transfer case actuator.

It drove great, no issues except for the dash light, which was annoying, and no DSC or ABS. I did it because I thought my transfer case was busted, though it just turned out to be worn-out fluid. I plugged it back in after changing the fluid and it drove fine.

The thread for the F3x cars is unfortunately irrelevant, the E9x cars have a different DSC/DXC system than the F3x cars. On the newer cars, the DSC module is the same between the xDrive and RWD cars and the difference can just be coded, but E9x cars have different hardware that can't just be coded off.

If you pull the front driveshaft, you have to worry about the stubshaft for the transfer case popping out. It might stay in there for a while but its only friction on the spline that holds in in there. That's actually why my X3 is currently RWD...I'm an idiot and pulled the stubshaft out by accident when I was changing the transmission fluid and dumped TC fluid out, then stripped the fill plug. I unplugged the TC to keep the TC from actuating and screwing itself up with low fluid. I have dash lights. It sucks. The car drives find though, I just don't have ABS or DSC.

As for doing the full conversion with the front subframe swap and everything...nice try, but the floor pan is different, and there's no way to mount a RWD transmission since the tunnel bulges out to make room for the transfer case, and that negative space there is where the crossmember for the RWD transmission mounts. You'd need some sort of custom mount to attach where the AWD crossmember mounts.
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      07-16-2018, 03:49 PM   #13
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Quote:
Originally Posted by motiv7891 View Post
Awesome feedback rothwem, I appreciate that. I actually suspected there were differences and coding might not even be a possibility, this kind of confirms it. As for a full RWD swap I agree, at that point you would seriously be better of ditching your xdrive for a RWD model.
Notice any positives with the car in RWD? I know there was no DSC or ABS but did it corner any better under power? acceleration any different since it was only driving the rear wheels or does it feel like it still wants to send it forward too? That would be a quick answer to the "is this even worth?" question...
It was pretty similar. I could steer with the throttle a bit more, though it wasn't dramatic. Clutch engagement was a bit different too, I can't really describe the difference, but I could feel a difference in the engagement point after I plugged the actuator back in.
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      07-16-2018, 03:53 PM   #14
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Quote:
Originally Posted by motiv7891 View Post
Alternatively, you could simply unplug your transfer case motor. In theory with the driveshaft disconnected the car can still try to send power to the front wheels. Now it will probably notice that it's not doing anything, think the wheels are slipping and send the power to the back again, but its still throwing power back and forth. I don't think you'll gain anything there.
Now, if you unplug the transfer case motor, the car cant move the power around at all so its gonna be stuck in rwd mode. IMHO this is really the only option for people that want to "play" like that as disconnecting a driveshaft still allows the car to send power forward, even if it's not going to the ground...meh
You WILL throw codes and your dash...well it may begin to look a lot like Christmas.
If you disconnect the plug for the transfer case, the DSC mdoule will notice this and throw an error. For safety reasons, any fault within the DSC system typically disables it. So power transfer will most likely not occur at all
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      08-14-2018, 11:59 AM   #15
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I removed the 30A fuses from both the DTC and transfer case circuits and the car is RWD. Sure, it has codes and the DTC is off, but the point was to have RWD to play and keep the car from robbing power due to traction issues. And believe the rear tires spin on demand.
It is awesome!!! I'm not leaving it forever and all I have to do is install the fuses to get it back if condition require. I bought an AWD for the Reno winters, so I don't want an RWD car all the time. You can't add 2 fuses to a RWD car and get AWD.
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      11-06-2018, 06:21 PM   #16
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Quote:
Originally Posted by TheGailWay View Post
I removed the 30A fuses from both the DTC and transfer case circuits and the car is RWD. Sure, it has codes and the DTC is off, but the point was to have RWD to play and keep the car from robbing power due to traction issues. And believe the rear tires spin on demand.
It is awesome!!! I'm not leaving it forever and all I have to do is install the fuses to get it back if condition require. I bought an AWD for the Reno winters, so I don't want an RWD car all the time. You can't add 2 fuses to a RWD car and get AWD.
Is this the same for a pre-LCI 330xi? Also, saw some things about wipers/turn signals/air bags not working when you do this... is this the case? Thanks.
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      11-07-2018, 11:05 AM   #17
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there's going to be a way to change the parameters for the awd system soon.

that's what you want.
no adverse affects, no physical changes.
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      11-07-2018, 05:44 PM   #18
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Quote:
Originally Posted by nsjames View Post
there's going to be a way to change the parameters for the awd system soon.

that's what you want.
no adverse affects, no physical changes.
I don't think there is much to change. Either the clutch is open and 100% goes to the rear, or locks up for 50/50. The multi variable stuff basically means the clutches are slipping. I think it's just BMW being evasive about how the system works.

For example to do a constant 70% rear/ 30% front, that means the clutches are not fully engaging and slipping. Some slip is OK but constant slipping will wear those clutches out.

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      11-07-2018, 05:51 PM   #19
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there's no slippage if the front and rear driveshafts are rotating at the same speed.

which is why BMW is adamant about tire circumferences being less than 1% different.

it's a wet plate clutch system, it's designed to slip without damage.
so you apply pressure, if the the wheel speed is different between front/rear the system is already preset to transfer toruq to the front axle. The DSC then varies the clutch pressure to vary the torque split based on wheel speed inputs.
It is not binary, it definitely has more than off and on.
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      11-07-2018, 06:37 PM   #20
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Hey guys sorry to threadjack but I wanted to ask a quick question;
So me being the dumbass that I am got completely different tire setup and I ended up running my transfer case into the ground, that thing literally popped.
So my question is, if I remove my front drive shaft, I know I’ll be RWD, but I’m wondering if my car is still going to function without the transfer case working correctly. Thanks.
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      11-10-2018, 06:21 PM   #21
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mechanically, no.
the electronics aren't going to like it too much.

if your case is physcally damaged then you need a new one. Even RWD the trans output still runs through the case. If it doesn't hold fluid or has wasted bearings or soemthing, you're still going to deal with that in RWD.
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      11-15-2018, 09:28 AM   #22
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Quote:
Originally Posted by M_spiels View Post
So I've been reading a whole bunch of different forums but no one has seem to ask the question. People say best way to go rwd is to remove the front driveshaft. I understand that just doing that makes it rwd and allows you to burn rubber and whatnot but thats not what im looking for. The awd system reduces power to the rear wheels by sending power to the front, my question is does it make more power to the rear wheels because you r essentially removing the power to the front wheel? Thanks in advance to anyone who can help me.
This might help you out, should be released December 18th. https://xdelete.app/xdelete_faq.pdf
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