7MT Noises
11-11-2016 | 12:40 PM
#16
Thread Starter
Three Wheelin'
Joined: Feb 2013
Posts: 1,406
Likes: 51
From: San Diego
This has been covered in another thread, sorry I couldn't find it, I tried 
First the sound: Are you referring to the thunk you hear after you engage the clutch at the moment you feel the gear engage? If so then this is most likely normal behavior - there are a lot of us with this issue (thus the other thread I couldn't find)
Possible cause: Remember that the 991 MT is based on the PDK transmission, as such it has two main drive shafts (not sure what the official name is, but you get the point), one for the odd gears and one for the even gears. When you approach a stop light, put the gear box in neutral and wait for the light, the drive shaft loses its spinning momentum and stops. Now when you engage first gear, with the clutch in, the gear synchros cause the drive shaft to spin up a bit, their synchronization and engagement is the 'thunk'.
The experiment: I found this interesting in my car, you need an open space to try this.
> Roll towards a stop in 2nd gear, slip the gearbox into neutral, come to a complete stop, push clutch, and engage 1st - I get a 'thunk' sound.
> Roll toward a stop in 3rd gear, slip the gearbox into neutral, come to a complete stop, push clutch, engage 1st - I get no 'thunk'.
> Roll toward a stop in 3rd gear, slip the gearbox into neutral, come to a complete stop, now sit for at least 30 seconds, push clutch, engage 1st - I get a 'thunk'
Note the YMMV: You may referring to a different sound, or your car may not has the 'feature' I described. But others have and it's been covered somewhere else in the depth of RL threads.
Happy hunting
First the sound: Are you referring to the thunk you hear after you engage the clutch at the moment you feel the gear engage? If so then this is most likely normal behavior - there are a lot of us with this issue (thus the other thread I couldn't find)
Possible cause: Remember that the 991 MT is based on the PDK transmission, as such it has two main drive shafts (not sure what the official name is, but you get the point), one for the odd gears and one for the even gears. When you approach a stop light, put the gear box in neutral and wait for the light, the drive shaft loses its spinning momentum and stops. Now when you engage first gear, with the clutch in, the gear synchros cause the drive shaft to spin up a bit, their synchronization and engagement is the 'thunk'.
The experiment: I found this interesting in my car, you need an open space to try this.
> Roll towards a stop in 2nd gear, slip the gearbox into neutral, come to a complete stop, push clutch, and engage 1st - I get a 'thunk' sound.
> Roll toward a stop in 3rd gear, slip the gearbox into neutral, come to a complete stop, push clutch, engage 1st - I get no 'thunk'.
> Roll toward a stop in 3rd gear, slip the gearbox into neutral, come to a complete stop, now sit for at least 30 seconds, push clutch, engage 1st - I get a 'thunk'
Note the YMMV: You may referring to a different sound, or your car may not has the 'feature' I described. But others have and it's been covered somewhere else in the depth of RL threads.
Happy hunting
One thing I noticed on this car that was kind of different for me was that it doesn't mind going into first at speeds under 10 MPH or so. And it doesn't like a rolling start in second from about 5...,not enough torque.
As a result, I find myself slotting it into first as I roll up to a stop, foot on brake, clutch depressed. If I can go quickly I go, or briefly hold the clutch. If it's a long wait, I'll shift to neutral and clutch out.
Perhaps it's because I am shifting to first while still in motion that when I shift to neutral and back into first that I've never heard a clunk?
As a result, I find myself slotting it into first as I roll up to a stop, foot on brake, clutch depressed. If I can go quickly I go, or briefly hold the clutch. If it's a long wait, I'll shift to neutral and clutch out.
Perhaps it's because I am shifting to first while still in motion that when I shift to neutral and back into first that I've never heard a clunk?
Thank you everyone for the replies.
11-11-2016 | 11:22 PM
#17
RL Community Team
Rennlist Member
Rennlist Member
Joined: Jan 2013
Posts: 8,947
Likes: 2,631
From: The Woodlands, TX.
Played around tonight and mine definitely clunks. Pretty light, but it's there. Totally eliminated b shifting to first while still in motion.
11-18-2016 | 07:36 PM
#18
Advanced
Joined: Mar 2010
Posts: 93
Likes: 37
From: Boulder, CO
I'm the one that posted that second thread. With 5k miles, mine still does it. If I wait just a second or two before easing into first, it doesn't clunk. Kind of annoying, but I've learned to live with it.
