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Originally Posted by UberRoo
One thing I would suggest be kept in mind is that the TCU does not have any sensors that are able to measure torque split. The readings given by the select monitor are only duty-cycle readings. A 10%, 50%, or 90% duty cycle does not necessarily mean you are getting 10%, 50%, or 90% torque transfer to the rear wheels. This is especially true if the transmission isn't in top condition, but even under the best possible circumstances, input values are not a good indicator of response. For example, half-opened valve does not mean only half the flow, or half pressure. In this example, if the plumbing is sufficiently large, a valve might need to be 90% closed to restrict any fluid at all. (Another example is the throttle valve in your car: the gas pedal. Ever notice how there isn't much difference between pushing the pedal halfway down and all the way down? There's a big difference between idle and 1/4 throttle, but not as much between 1/4 and 1/2, and almost no difference between 1/2 and wide open.)
I strongly suspect that the 90/10 and 50/50 figures are very much closer to the truth. I'd wager that even the slightest activity of the duty solenoid would necessarily cause at least a 90/10 torque split. It would be very difficult to modulate less than that. Even disabling the solenoid completely might not reduce torque split less than that. I'd also wager that the torque split does not increase significantly until the duty cycle reaches the upper 90% range. In these upper ranges, the degree of control would be marginal and it would be difficult to regulate torque split. In this upper range, torque split would probably be mostly 49% and 50%.
Although the TCU makes great efforts to precisely control the torque split, I think the reality is that it's mostly just on or off. Quite frankly, there's no large fault with that. It works very well that way.
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UberRoo,
What you're saying makes good sense in theory, but is hard to prove in reality.
I've posted my results using the SSM when in the awd diagnostic mode. The excerpt I posted at the start of this thread from the Road & Track Guide about the multi-plate transfer clutch seemed to reiterate these findings.
If you or Harv can think of an elegant way to show the torque split is closer to 90/10 than 60/40 in normal driving (with no braking, acceleration or steering inputs affecting transfer) then by all means prove these results wrong.
-Chike