facelift/pre-facelift & 1/2 model years??

[TiAgX5]

Originally Posted by PropellerHead

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.

It does so dynamically 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.

[PropellerHead]

Originally Posted by TiAgX5

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?

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.

[TiAgX5]

Originally Posted by PropellerHead

I am saying that a fixed, split-ratio, gear-driven transfer case (like the NV 124 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 NV125 models are chain driven with a clutch system that allows this to vary up to 100%. It just does.

I guess Sir Issac Newton was wrong. 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.

[PropellerHead]

Originally Posted by TiAgX5

I guess Sir Issac Newton was wrong. 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.