Quote from: metroplex on September 03, 2016, 09:09:49 PM
So the electronic clutch mechanism is in contact with the RdU gear oil?
It doesn't seem to be actually part of the differential fluid system: http://www.shoforum.com/index.php?threads/how-does-the-awd-work.119781/
Here some info on the AWD for your reading pleasure. Z Police-only Cooling
The police version of AWD has three unique features to improve durability during severe use. First, the Power Transfer Unit on the AWD system uses a police-only auxiliary cooler. The retail AWD unit is air cooled, i.e., the aluminum housing dissipates heat to the surrounding air. When the vehicle is stationary, the amount of cooling is obviously less than when the vehicle is moving.
On the police AWD unit, the front housing of the Power Transfer Unit has a special water jacket cast into the assembly. The integral PTU auxiliary cooler is part of the water cooling system. That means the cooling remains "active" since the cooling water is constantly circulated, whether the police vehicle is moving or stationary.
The PTU cooler is plumbed into the bottom of the radiator, where the water is cooler than at the top of the radiator.
Second, the Power Transfer Unit uses an internal temperature sensor, not found on the retail unit. A module keeps track of oil temperature in the PTU and the amount of time spent at that temperature. An electric clutch pack engages and disengages as torque is transferred to the rear wheels.
Both the PI Sedan and PI Utility default to FWD under normal conditions. As the front wheels slip, torque is selectively diverted to the rear wheels. A time versus temp logarithm activates an Oil Minder light in the driver message center if and when it is time to change the PTU fluid. The special synthetic oil may last 100K miles in normal police use.
Third, the Rear Differential Unit on the police version uses a fluid-filled clutch pack, while the retail version uses dry clutches. The fluid-filled RDU can withstand more severe duty.
The cooling ability of the police-only auxiliary radiator-water jacket combination was tested in 110 deg. F weather. Hard driving—where power is constantly shifting from front to rear, back and forth—can take many different forms.
Think aggressive driving during a city pursuit: hard throttle for a city block, 90-degree turn, hard throttle, where torque definitely shifts from front to rear. Also think getting unstuck in desert sand. Even though the vehicle and wheel speeds are not high, torque is constantly shifting between the front and rear spinning wheels.
Under the worst conditions of high-torque, clutch engagement and disengagement, the synthetic oil reached temperatures around 195 deg F. The special lube is rated for temps just over 500 deg F. The air-to-water cooler works.
http://www.hendonpub.com/resources/article_archive/results/details?id=5091