All Wheel Drive Rx 330..how It Works

[rfcbuf]

My '04 RX 330 has all wheel drive but I can't find any description of how the system functions. Is it running on 2 wheel or 4 wheel drive at all times or 4 wheel drive only when conditions warrent the full 4 wheel function? Also is the power transmitted by transfer case via vicious coupling or is it fully mechanical? Really want a description of how it works in laymen's terms. No lexus brochures have any information.

[GDixon]

wwest should be here any moment to explain.

You might search his posts and you will most likely find the answer to how the RX AWD transmission functions.

Check out this post to get you started.

http://us.lexusownersclub.com/forums/index...showtopic=42997

[wwest]

wwest should be here any moment to explain.

You might search his posts and you will most likely find the answer to how the RX AWD transmission functions.

Check out this post to get you started.

http://us.lexusownersclub.com/forums/index...showtopic=42997

Mechanically the RX330 AWD system uses three simple open diff'ls, front, center, rear. Open diff'l's will distribute engine torque equally as long

as all four tires have roughly the same traction. The problem with that arrangement is taht if one wheel loses traction and begins to spin freely that will severely limit the torque available to all the other wheels and you will be STUCK.

To help prevent that from occurring (sometimes) the RX330 uses traction braking as "backup" to simulate the functionality of an LSD, Limited Slip differential. It does that by using the ABS wheel speed sensor to detect that a wheel or wheels are spinning inordiantely fast with reference to other wheels and then applies braking to the wheels that have lost traction in order to sustain a high(er) level of engine torque for distribution to the wheels that still have traction (hopefully).

This is clearly a compromise solution, not satisfactory in all circumstances, certainly not when compared to true 4WD or 4X4 functionality, and not even many other AWD systems such as the BMW X3/5 or the Honda/Acura SH-AWD system.

Lexus is currently advertising that the newer RX350 has re-adopted the VC, Viscous Coupling, just as they did early on with the RX330 (which proved to be "miss-information") as is likely the case with the RX350. The RX350 shop/repair manuals indicate that it has the vary same PTO, Power Take Off, transfer, as the RX330.

I understand the newer vehicles have the ability to turn TC, Traction Control (the braking implemented LSD/AWD system) off, a definite improvement.

[300gone330]

Thanks for the layman's breakdown WWEst....this was an awesome post!