The Getrag Powershift dual-clutch semi-automatic gearboxes are split into two main types:
- Wet Clutch (Includes 6DCT450) (6DCT470)
- Dry Clutch (Includes 6DCT250)
Brands to use this dual-clutch transmission include Chrysler Ford Fiat Jeep Mitsubishi Landrover Volvo, and it may be coded as DCT450 – DCT470 – MPS6 – W6DCA – C635 – SST EVO X or Powershift.
The operation of a dual-clutch transmission is similar to two traditional manual transmissions, each with its own clutch, operating in parallel and alternating shifts.
The Powershift unit is a six-speed with one clutch acting on first, third and fifth gears, and the other used for second, fourth, sixth, and reverse gears. As first gear is engaged, the 2-4-6-R clutch is disengaged, and the second gear cogs are engaged. At the appropriate time, the 1-3-5 clutch is disengaged, and the 2-4-6-R clutch is engaged. While in second gear, the other side shifts from first to third. The process is repeated with none of the efficiency loss commonly associated with torque converters and, in theory, provides quick smooth shifts.
In-car servicing consists of an oil drain and external cartridge filter replacement, an oil meeting DCT specification is required. Complete fill is approx 7.5 litres. Service drain refill is approx 5.5 litres.
Due to the wet clutch and gearbox sharing the same oil, Powershift transmissions require regular servicing. Approximately every 40,000 KM to help prevent a blocked internal filter and failures due to fluid contamination.
Common symptoms of a faulty 6DCT450
- Harsh/Banging into 1st & reverse gear – Delayed selection of 1st & reverse gear – Shuddering.
- Clutch slipping – Vehicle speed not increasing on acceleration – Jolting motion on gear changes.
- Vehicle stalling – No drive -Transmission malfunction service now warning light on dashboard.
Please note you may experience some, but not all the listed faults depending on the level of damage internally.
Mitsubishi Evo X SST also is known as DCT470, can suffer from the plastic 2/4 selector fork failing (circled in red) this can be rectified with the replacement billet fork shown below:
Powershift DCT450 can suffer from failed plastic damper spring retainers.
Replacement retainers and oversize retainers to remove spring free play are available.
- Common replacement parts that can only be replaced on bench overhaul are the dual-clutch assembly the internal filter vehicle speed sensor and the Mechatronic unit.
- Dual Clutch replacement requires specialised tools to achieve pinpoint accuracy in clutch set up to avoid re-works, faulty operation or damage to other components.
Mechatronic related failures are common with this unit. Many failures are related to fluid contamination. Normal wear and tear from the operation of the dual wet clutch assembly and the gear train deposits clutch material and metallic debris in the fluid. If the transmission fluid has excessive contamination, and the Mechatronic has been diagnosed to be faulty, the unit must be removed, disassembled and cleaned. This must be done even if there are no other concerns. Failure to do so will cause a repeat failure of the Mechatronic assembly! The control solenoids and control valves will become contaminated and will malfunction. The magnetic sensors will pick up loose, ferrous material in the fluid, causing the shift shaft position sensors and speed sensor signals to fail.
Driveline are Australian distributors for Dodson Motor Sport world leaders in DCT performance parts with a range covering a wide variety of performance vehicles including Nissan GT-R, Mitsubishi EVO X, Porsche PDK, VW and Audi DQ250 and DQ500, Audi R8 and the ‘insane’ Lamborghini Huracan find us at http://www.drivelineap.com.au