The transmission in the 2001 four-wheel drive RX 300 features an integrated transfer case and a viscous center differential that provides a 50/50 front-to-rear power split. The system requires no activation by the driver. If slippage occurs at the front or the rear, the viscous center differential automatically and transparently directs power to the wheels with the most traction. The traction control provides further "fine tuning" by sensing individual wheel rotation speeds and braking the appropiate wheel when necessary. The fact that the 4wd system on the RX is supplying torque to both axels all the time gives it superior handling characteristics to other so-called AWD systems where only one axel has torque until slipagge occurs. These are "reactive" systems, the RX is a "proactive" system.
Couldn't have stated it better, nice job.
Search General Questions