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Have a new 2024 C8 now with a 1000 miles on it. When using cruse around 38 mph and in auto the DCT is in 6th gear and the tach varies a couple hundred rpm. If I select manual tach is rock solid. I have had a couple of Audi with DCT and auto is no different than manual. My dealer said this was normal. I question his comment. Any input would be appreciated.
Have a new 2024 C8 now with a 1000 miles on it. When using cruse around 38 mph and in auto the DCT is in 6th gear and the tach varies a couple hundred rpm. If I select manual tach is rock solid. I have had a couple of Audi with DCT and auto is no different than manual. My dealer said this was normal. I question his comment. Any input would be appreciated.
There is no slipping in a properly functioning DCT. If the speed is constant, and the gear does not change, the RPM should not change. If the RPM change you are seeing is coincident with a slight speed change, then its not slipping. In 6th gear, a 250 RPM change would be about 8 mph. I notice you siad 6th gear and 38 mph. That very close to what some would say is lugging the engine. I calculate about 1155 RPM give or take. According to the table in manual, an upshift to 6ht gear should not even be allowed until 39 mph. Are you sure its not shifting when you see the RPM change? You should not see an RPM change even if V4 kicks in unless there is also a speed change.
The clutches briefly release during transition in & out of V4 to keep things smoother. Watch your tach and you'll see it.
Ok. I was aware of what was described a "microslip" to help dampen the transition. Did not know and never saw where it resulted in a noticeable change in RPM. That's a new one to me. I must concede I have never watched for that. I can tell when the transition happens but I am never looking at the tach.
[QUOTE=Andybump;1607517857]There is no slipping in a properly functioning DCT. If the speed is constant, and the gear does not change, the RPM should not change. If the RPM change you are seeing is coincident with a slight speed change, then its not slipping. In 6th gear, a 250 RPM change would be about 8 mph. I notice you siad 6th gear and 38 mph. That very close to what some would say is lugging the engine. I calculate about 1155 RPM give or take. According to the table in manual, an upshift to 6ht gear should not even be allowed until 39 mph. Are you sure its not shifting when you see the RPM change? You should not see an RPM change even if V4 kicks in unless there is also a speed change.
[/QUOTEMaybe it was in 5th. Flat ground with no speed change. Definitely can hear an engine sound change as tach varies. I will check to see if it is doing a V4 change]
There is no slipping in a properly functioning DCT. If the speed is constant, and the gear does not change, the RPM should not change. If the RPM change you are seeing is coincident with a slight speed change, then its not slipping. In 6th gear, a 250 RPM change would be about 8 mph. I notice you siad 6th gear and 38 mph. That very close to what some would say is lugging the engine. I calculate about 1155 RPM give or take. According to the table in manual, an upshift to 6ht gear should not even be allowed until 39 mph. Are you sure its not shifting when you see the RPM change? You should not see an RPM change even if V4 kicks in unless there is also a speed change.
[/QUOTEMaybe it was in 5th. Flat ground with no speed change. Definitely can hear an engine sound change as tach varies. I will check to see if it is doing a V4 change]
Ok, yeah 5th would seem more likely. As you saw there is some evidence that it could be the transition from V8 to V4 because of the clutch slippage that occurs with the purpose of damping the vibration. Is it a brief RPM change? Are you using the digital tach readout? I use the graphic version, but if I am in the situation where V4 is kicking in, it means I'm just cruising and I would not be looking at the tach anyway. I'v never noticed the RPM change, but I can sense the transition. Many cannot - and some will insist the nobody can. Its a pretty subtle change in vibration and sound, I notice it more with the top down - probably because there is an exhaust note change when the AFM valves close.
DCT Slipping
