04/12/2024
DCT transmissions shift when the corresponding clutch is disengaged. This means that whenever a shift occurs, there will be no torque transferring through the drivetrain. The only job of a synchronizer is to slow down or match speeds of the shafts to the desired gear change. So, a well engineered/designed DCT with adequate synchronizers should last the life of the vehicle if properly maintained. This 2013 Porsche 911, owned by Peter, was brought to SDM because every other shop was scratching their heads. With no fault codes stored in the TCM or DME, this required outside tools. After applying an oscilloscope (yellow line clutch press one, blue clutch press two) to the clutch pressure sensor, we were able to monitor if both clutches were engaged momentarily at the same time. We found that the TCM had an internal failure and was briefly allowing the corresponding clutch to be energized while the transmission was attempting a shift. So, in other words, when a DCT vehicle accelerates from 50mph, the transmission will shift from six, then 5th, then 4th, then 3rd, and then 2nd. When the transmission was attempting to shift the fork into the 2nd gear slot, clutch 2 (blue line) had momentary spikes, which would make the car drive clunky and wear the 2nd gear synchronizer prematurely and so on for 3rd gear. So, in Peter's situation, the cause was the TCM, and the effect was the 2nd and 3rd gear synchronizers. The full repair required a complete disassembly of the PDK, replacement of 2nd and 3rd synchronizers, and a new TCM with the latest software. We are happy to say that Peter's response was and I quote “My car has never driven this smooth since I have owned it for the last 7 seven years” This repair was performed by SDM in August of 2023 and has been performing perfectly since then. Video coming soon.
