It may transfer there to fill the gap between the 0-38% (Front) or 0 - 62% (rear) of power delivered, but it cannot (and does not) vary on the older cars. The power doesn't 'go' anywhere- except away. The DSC system cuts the power if it exceeds the available traction that either axle can use.

Power is transferred dynamically (and electronically as opposed to physically) from 0-100% for either axle on XDrive.

So in summary, you saying that when the rear brakes lock the rear wheels there's no more then 38% total torque from the transmission twisting the front wheels?

You do realize that if you try to explain it does not go to the front wheels, you are, in fact stating, BMW has negated Newtons first law of energy......Energy can neither be created nor destroyed in a closed system.

I am saying that a fixed, split-ratio, gear-driven transfer case (like the NV 124 and NV 125 in non-Xdrive vehicles) will output power at a fixed ratio front to rear. That torque transfer ratio is 38 front, 62 rear and it is constant, not variable.

Electronic nannies (like DSC) and zillions of hypothetical situations can do what they want, but the physical gears and the static behavior of the NV124 cannot be changed. It just can't.

XDrive equipped models (ATC 500) come with a clutch system that allows this to vary up to 100%. It just does.

Edited to correct part numbers.

I guess Sir Issac Newton was wrong.:yikes: I guess the torque to that gear must take a bus to Hoboken, NJ or something like that.


The torque ratio is fixed ONLY as long as both front and rear gears are turning at the same rpm. When one gear is slowed or stopped the torque supplied to that gear transfers to the other gear in this universe.

Where did I say that the TQ goes anywhere outside of the planetary gear? You're a little anxious.

Read again. I said it transfers and it does it at a fixed ratio. The gears turn at a 1:1 ratio- that is one spins at the same speed as the other. One has more teeth- the rear- and spins slower but with more teeth resulting in a higher ratio- all the time- than the other (the front)- that is smaller but with fewer teeth driving output. (I am prone to get the speeds/teeth mixed up, but the concept of a fixed ratio is the same despite my spatial deficiency) The gears spin at the same speed, but are different sizes resulting in different output front vs rear.

There is no clutch to vary the output of power within the transfer case on a non-XDrive car. Both spin at the same input/drive speed (1:1), but the output is different bc they're different sized gears. See below for an illustration.

Good to know. Anyway, here are the details of my build sheet.
Type code FB53
Type X5 4.4I (USA)
E series E53 ()
Series X
Type GEFZG
Steering LL
Doors 5
Engine N62
Displacement 4.4
Power 235
Drive ALLR
Transmission AUT
Colour TITANSILBER METALLIC (354)
Upholstery LEDER DAKOTA/SCHWARZ (LCSW)
Prod.date 2003-09-26
Automatic transmission
Sports suspension settings
Sports leather steering wheel
BMW LA wheel, star spoke 132
Sports package
Roof railing
Fine wood trim
Smoker package
Sports seat
Rain sensor
Preparation f tel.installation universal
CD player
Headlining anthracite
White direction indicator lights
High speed synchronisation
Spare wheel
Self-levelling suspension
Multifunction f steering wheel
Alarm system
Exterior parts in vehicle colour
Windscreen, green-tinted upper strip
Drink holder
Seat adjustment, electric, with memory
Xenon Light
Air conditioning, rear
Automatic air conditioning
BMW US Radio
Radio BMW Business (C43)
HiFi speaker system
Preparation, BMW 6-CD changer I-bus
Acoustic fasten seat belt reminder
Description (EPC)
Language version, English
Radio frequency 315 MHz
Control of number-plate attachment

I'm thinking mine looks pretty close to that ...
http://www.xoutpost.com/members/haumana-albums-x.html

I think the important point of the DSC/traction control 'discussion' is that if I had Xdrive I would have a better chance getting through a mud pit or getting around a curve instead of going off into the woods.

Limiting this post to braking of a wheel(s) and how fast a wheel is turning----

The original system does split 100% of the power mechanically--can't change. The front wheels spin with 32% of the available power and the rear are pushing with 68%, all the time, in all circumstances. When the fewer sensors of the original system indicate I have a problem it will brake a wheel or wheels. The same percentages (32% front, 68% rear) of the total power available is still going to each end. It is just that the braking system is restricting some percentage of that power from getting to the ground at one or more wheels. No matter the input of the monitoring sensors, no wheel is spinning faster than the mechanical split of total power. The resulting assistance can only make a wheel(s) spin slower.

The Xdrive has more sensors so it would add more talent to mine. The Xdrive system also regulates the power to wheels electronically rather than mechanically. That's the reason for the clutches. In theory, one wheel could take 100% of the total available power. Xdrive can speed up or slow down any single wheel or combination of wheels.

A very talented driver on a road course will go faster without either system. I turn it off if I want to know if my commitment ends before the grip. For maximum straight line acceleration I shut my system off. I would never turn off either system for day to day driving.

I believe two of us agree with each other. :thumbup:

Except maybe the mud pit. As someone who's been IN a mud pit when I ran off the interstate, I think you'd have a better chance with non XDrive than with it. The reason is that XDrive is too smart for it's own good in that situation. If no wheels have traction, it'll squat. It pouts and wants to take its toys and go home. In fact, the only way I got out of the mud was to disable the system (DSC) and let the wheels spin whether they had traction or not. It was hair raising, but effective. It's this intelligence that works great in every day driving- spreading power all around all the time- but not so well in extreme situations like the snow in the video above.

I will add that X Drive not only uses braking like the earlier system, but it interfaces with the entire DSC. It senses all factors of the system to relay information to the clutches. The advantage here is that it does not have to 'wait' for wheel slip to apply brakes and then 'transfer' power (L/R, of course) like the earlier systems. It's looking for much more than just wheel spin/slip/speed variation.

XDrive and the clutches can nearly 'predict' (1/10 of a sec) what axle will need power, which one will need less, and send the power there based on inputs from ABS sensors, vehicle yaw/pitch, steering position, wheel speed, throttle position and every other sensor the DSC is monitoring. The two are in constant communication with one another with a reactive time that is so quick, it seems nearly proactive. BMW brought this enhanced level of communication to the S(a)V platform in 2004 before anyone else. Add some Eibach's to it and you'll outrun more people in the twisties than you did before. ;pimp;

Having said that, I still enjoy my mother in law's 2001 3.0. It's sneaking up on 13 years in service. Nary a whisper beyond regular maintenance.

Well if doesn't help in a mud pit I would rather keep what I have. I go every weekend--mud, beer and wet tee shirts--what could be better?

Yes, all the other stuff the Xdrive measures I summarized in more sensors as my pea brain gets confused easily.

It's a good thing that these technologies never go wrong, go wrong, go wrong, go wrong----please reboot there has been a critical error.