I do aplologize if this is in the wrong section,figured might benefit somewPolice-Only Power Transfer Unit
Since the Power Transfer Unit operates all the time to spin the driveshaft to the rear, the PTU can get hot. On the police version, a number of steps are taken to assure reliability and durability in police use. First, a cooler is added to the front of the PTU housing. The police-only PTU housing has an integral water jacket connected with water lines that run to the bottom three coils of the radiator. The jacket receives engine coolant from the radiator to maintain the correct PTU oil temperature.
Second, the PTU has a gear lube temperature sensor. A module keeps track of the gear lube temp, and how long / how often it was at that temperature. When a threshold is reached, a change PTU Oil light activated.
Finally, the AWD system has a two-stage way to protect itself from damage during extreme, prolonged use. The ATC as a heat protection strategy based on a number of factors, including wheel speed and duration of activity, to determine if overheating is occurring. If the ATC detects overheating, it will lock the clutches together to cool them. Clutches that slip to provide partial torque transfer get hot from the friction of the slippage. Locking the clutches stops the slip and cools the entire unit. In a locked condition, power is transferred to the rear wheels.
If the temp continues to rise even in a locked condition, the PCM disables the coupling altogether. The vehicle operates only as a FWD. AWD OFF is displayed. On the Police Interceptors, the PCM will automatically exit heat protection mode and clear the AWD OFF message when the temp returns to normal. This whole process is sped up by turning the ignition off and allowing the vehicle to cool for 10 minutes.
The ATC/RDU used on the Police Interceptors uses fluid-filled "wet" clutch packs. The retail Taurus and Explorer use dry clutches. The PI wet clutches can withstand higher temps and withstand higher temps longer than the retail unit. The ATC and RDU are not field serviceable. In case of a problem with either system, the whole unit is replaced.hat. Z
