Basically correct except that the dual pump rear diff that makes the AWD kick in (yo) is an entirely mechanical system, no "speed sensors" required!
zak410,
Jun 29, 12:17am
and it works very well; I live at the end of a metal road, 10km, and as soon as a front wheel try to spin, the back wheels come on; hardly noticeable too; probably because of it, I never owned a car where to tyres last as long.
jsbike,
Jun 29, 12:20am
dual pump, when all wheels go the same speed, front diff turns its pump and rear diff turns itspump the same speed so pressure is equal in both, when the driving wheels slip (wheel spin), their pump drives faster and makes more pressure than the non slipping wheels. When one diff makes more pressure in its pump than the other, the pressure imballance is used to engage a clutch that engages 4wd. i think. simple but effective.
ralphdog1,
Jun 29, 4:04am
Pedantic I know, but aren't the pumps in the rear diff on either side of the clutches that the pressure contols!
jsbike,
Aug 11, 8:43am
one pump driven by the drive shaft from the transfer case at the front of the vehicle, and the other driven by the rear differential. When there is a pressure difference of greater than 3% between these two pumps, a clutch that connects the front and rear axles begins to engage gradually, the more the fronts slip, the more that clutch engages. Seems a good system, my cefiro has to have a 5% front/rear speed difference before it engages the fronts
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