Subtle Clunk when Shifing into 1st Gear
03-24-2011, 11:04 PM
#1
Subtle Clunk when Shifing into 1st Gear
Hey all,
I'm a proud new owner of a 2007 Galaxy Gray GT. Will post pics later and give a proper introduction.
But for now have to ask this question...
When shifting into first from neutral at a stop, I hear and feel just a slight clunk. That is, when starting from a stop, clutch in, shift into first from neutral, and as I'm doing this motion feel the clunk, let out clutch and give gas, everything's fine.
With a little experimentation, I think it's the clutch not fully disengaging even though the clutch pedal is fully depressed. Once I get the clunk, I can shift through all gears easily (with clutch pedal depressed), including first. However, if I let the clutch back out while in neutral, and then repeat clutch in and shift into first, I get the clunk once more, which sure feels like it's the clutch plate finally fully disengaging.
Anyone else get this? Is it a sign of a problem? No other trans issues at all--just this.
TIA
I'm a proud new owner of a 2007 Galaxy Gray GT. Will post pics later and give a proper introduction.
But for now have to ask this question...
When shifting into first from neutral at a stop, I hear and feel just a slight clunk. That is, when starting from a stop, clutch in, shift into first from neutral, and as I'm doing this motion feel the clunk, let out clutch and give gas, everything's fine.
With a little experimentation, I think it's the clutch not fully disengaging even though the clutch pedal is fully depressed. Once I get the clunk, I can shift through all gears easily (with clutch pedal depressed), including first. However, if I let the clutch back out while in neutral, and then repeat clutch in and shift into first, I get the clunk once more, which sure feels like it's the clutch plate finally fully disengaging.
Anyone else get this? Is it a sign of a problem? No other trans issues at all--just this.
TIA
Last edited by devtec; 03-24-2011 at 11:55 PM.
03-25-2011, 01:35 PM
#4
Thanks... looks like it is not the clutch pedal bracket, and it definitely is not just the gears clicking into place.
It is specifically that the clutch is not fully disengaging even with the pedal depressed, as evidenced by the small jolt I feel when trying to select first gear from neutral. It is as if the clutch has trouble disengaging from the layshaft in neutral even with the pedal fully down. Anyone else encounter this?
It is specifically that the clutch is not fully disengaging even with the pedal depressed, as evidenced by the small jolt I feel when trying to select first gear from neutral. It is as if the clutch has trouble disengaging from the layshaft in neutral even with the pedal fully down. Anyone else encounter this?
03-25-2011, 04:03 PM
#5
Registered
nah its normal. my S2 does that too. very faint donk sound.
what it is the syncro trying to stop the input shaft and the force gets sent to the drive shaft and rear diff. the sound is made by the slack in those components.
what it is the syncro trying to stop the input shaft and the force gets sent to the drive shaft and rear diff. the sound is made by the slack in those components.
07-21-2011, 11:08 AM
#16
Try this... with the car running in neutral and your foot off the clutch, depress the clutch and quickly shift to first. Car tries to move a little and you hear a small clunk right... it's the syncro doing its job which is to make the input shaft match the speed of the output shaft. This transmits a very small amount of energy to the output shaft and consequentially the rear wheels when the input shaft is suddenly stopped from moving.
Now with the car running in neutral, depress the clutch and count to 10. In the time it takes you to slowly count to 10, the input shaft will come to a stop on its own. Now shift the car into first. No movement right? It's because while the clutch pedal was depressed the input shaft stopped and wasn't suddenly stopped from spinning by the syncro, it was already stopped when you shifted into gear.
07-21-2011, 11:26 AM
#19
In the context of this particular conversation, though, the OP has already pushed the clutch pedal all the way to the floor. What is supposed to happen at that point?
07-21-2011, 12:00 PM
#20
The other thing that makes me believe this is what's happening is that he mentioned that if he depresses the clutch and moves through some gears and back to first, the clunk is no longer there. This would have allowed time for the input shaft to come to a complete stop.
Last edited by Arca_ex; 07-21-2011 at 12:02 PM.
07-21-2011, 01:34 PM
#21
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Mine does this too, and its almost definitely the input shaft.
Let me try and help with a diagram, This is your drivetrain:
Engine}------|Clutch|--------|Synchros and Gears|------------{Diff and wheels
..............^Flywheel......^Input Shaft..............................^Drive Shaft
So if your engine is spinning, clutch engaged, trans neutral, Your input shaft is spinning with your engine at idle. Then when you clutch out, the Input shaft isnt connected to anything, but still spinning. Then when you put it in gear, the input shaft has to stop, because your hooking it up the diff and wheels which arent moving (youre at a stop). The gears smacking into place and taking up all the slack in the driveline is the clunk.
This is also why some people choose to double clutch (engage the clutch in neutral) on shifts with large RPM changes. You can spin the input shaft up to the right speed to match to take work off the synchros and extend their life.
(Without double clutching, the engine might be rev matched, but the iput shaft would still be spinning at the speed the engine used to be running)
I hope this helps.
Let me try and help with a diagram, This is your drivetrain:
Engine}------|Clutch|--------|Synchros and Gears|------------{Diff and wheels
..............^Flywheel......^Input Shaft..............................^Drive Shaft
So if your engine is spinning, clutch engaged, trans neutral, Your input shaft is spinning with your engine at idle. Then when you clutch out, the Input shaft isnt connected to anything, but still spinning. Then when you put it in gear, the input shaft has to stop, because your hooking it up the diff and wheels which arent moving (youre at a stop). The gears smacking into place and taking up all the slack in the driveline is the clunk.
This is also why some people choose to double clutch (engage the clutch in neutral) on shifts with large RPM changes. You can spin the input shaft up to the right speed to match to take work off the synchros and extend their life.
(Without double clutching, the engine might be rev matched, but the iput shaft would still be spinning at the speed the engine used to be running)
I hope this helps.
07-21-2011, 02:12 PM
#22
After I installed my short shifter I'm able to hear the input shaft of the transmission spinning, and when I press the clutch pedal to the floor it takes about 1-2 full seconds for the input shaft to come to a complete stop. So if you were to press the clutch pedal to the floor and immediately put it into first, the input shaft would still be moving when 1st gear is being engaged. I saw that the OP mentioned that the clutch pedal was being pushed to the floor but I didn't see anything about how fast he's shifting to first after pushing the clutch pedal.
The other thing that makes me believe this is what's happening is that he mentioned that if he depresses the clutch and moves through some gears and back to first, the clunk is no longer there. This would have allowed time for the input shaft to come to a complete stop.
The other thing that makes me believe this is what's happening is that he mentioned that if he depresses the clutch and moves through some gears and back to first, the clunk is no longer there. This would have allowed time for the input shaft to come to a complete stop.
Would the real answer to his question/concern not involve swapping trans fluid (as others have suggested) but to simply wait a second or two for the input shaft to slow down before making that initial engagement into first gear?
As for my own opinion; I would not call this characteristic "normal", but something that we all should accomodate so as to limit future transmission issues.
Last edited by Charles R. Hill; 07-21-2011 at 02:16 PM.
07-21-2011, 02:53 PM
#23
Precisely. The short shifter really allows us to hear what is going on inside the transmission, doesn't it?
Would the real answer to his question/concern not involve swapping trans fluid (as others have suggested) but to simply wait a second or two for the input shaft to slow down before making that initial engagement into first gear?
As for my own opinion; I would not call this characteristic "normal", but something that we all should accomodate so as to limit future transmission issues.
Would the real answer to his question/concern not involve swapping trans fluid (as others have suggested) but to simply wait a second or two for the input shaft to slow down before making that initial engagement into first gear?
As for my own opinion; I would not call this characteristic "normal", but something that we all should accomodate so as to limit future transmission issues.
07-21-2011, 03:17 PM
#24
Yeah changing trans fluid won't do anything about it. Mine did it with the stuff Mazda uses and with Red Line MT-90. I don't think it's particularly harmful to the transmission since it's just the synchros doing what they were designed to do, but waiting a couple seconds for the input shaft to stop spinning may help lengthen the life of the 1st gear synchro so that doesn't hurt either.
