Car moves with clutch pressed - Pontiac GTO Forum
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post #1 of 9 (permalink) Old 06-06-2005, 04:18 PM Thread Starter
 
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Car moves with clutch pressed

My car has 1200 miles on it and I've started to notice that the car moves slightly forward when moving shifter into first. The movement is very slight; almost a rocking motion forward. Once all the way into first, the car does not move. Happens only when first moving the shifter to first but before it's all the way into first.

Dont know if it's related, but I also have the reverse issue as well as sometimes not wanting to go into first. Also, I can feel what feels like a clutch slap, for lack of a better description, through the shifter when I sometimes press the clutch.

Anyone ever experience this? I've never had a car that moved like this with the clutch fully pressed. Any ideas on what it might be?

Have the car at the dealer now to address this as well as what appears to be a leaking battery.

Thanks for any info!
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post #2 of 9 (permalink) Old 06-06-2005, 04:59 PM
 
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Mine does that, as far as I know its just the gears moving to get the teeth to mesh. It was weird for me the first time though. It doesnt happen every time, seems to be only under the circumstance where the gears are not lined up in first.
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post #3 of 9 (permalink) Old 06-06-2005, 05:11 PM Thread Starter
 
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I just cant believe this is normal. I can pretty much duplicate it each time, but only the first time I put it into first after pressing the clutch. If I take it out of first with the clutch still pressed then put it back into first, it doesnt move. But if I take my foot off the clutch with it in neutral, then press the clutch back in again and go back into first, it moves.

Are you also having problems putting it into first or reverse? Im thinking these have to be all related in someway. Wish I knew enough to know what was going on in there!

Talked to the svc advisor and got the usual can't duplicate. Will have to go in tomorrow and show them myself.
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post #4 of 9 (permalink) Old 06-06-2005, 06:45 PM
 
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This is normal with manual transmissions. Though it is not as noticeable from one vehicle to another because of varying vehicle weights, rolling resistance, rotating mass and other things that I'm sure I am not thinking of. What is happening is that when the vehicle is running in neutral with the clutch out the clutch disc, transmission input shaft, upper shaft and sometimes a gear on the lower shaft are all spinning with the engine. When you depress the clutch all of these parts continue to spin for some time because of inertia. When you put it in gear the synchro tries to match the input speed to the 1st gear so as not to grind the teeth as it was designed to do. So all that inertia is transferred into a momentary surge of forward movement. When you take it back out of gear and try to duplicate it without cycling the clutch again, it does not happen because the previously mentioned parts were stopped the first time you put it in gear.
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post #5 of 9 (permalink) Old 06-06-2005, 10:09 PM
 
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What he said.......!!
QS05GTO, I dont have a problem with reverse (though I dont use it very much obviously) but I do have problems with getting the car into 1st once in a while. I have found this to be due to the gear mesh again. It has become my habit to depress the clutch and put it in 2nd and then first (just a quick down and up) to align the gears. Not sure if its a "problem" or just the brutish nature of a big a** gearbox like the T-56. This seems to occur more when I end up coasting to a stop in neutral with the clutch engaged and then disengaging the clutch to shift to first when its time to go. You may find that it never happens if you put into first while the car is still moving forward a little bit so the gears can sync easily.
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post #6 of 9 (permalink) Old 06-06-2005, 10:42 PM
 
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Fellas, if I understood you correctly, what I think you're describing is clutch disc stick. Meaning, if the clutch sat engaged for some, even a relatively short, period of time, on some vehicles one side of the disc facing sticks to the flywheel surface, even though the pressure plate has moved off the disc. Usually it happens if there's excessive friction between the input shaft spline and the clutch disc hub (for whatever reason). Once you engage a gear with the shift lever the transmitted torque should jolt the system and shake the disc off the flywheel into its free position. Often this is the result of an overly tight fit between the disc hub and the input shaft spline and in addition possibly due to some driveline mislalignment. The tight fit is generally chosen to reduce the lash between the two parts and limit the driveline snatch during parking lot maneuvers and generally reduce driveline noises at low torque conditions. Still, should not be happening though.

If I misunderstood the condition you're experiencing, my apologies.

Last edited by PWR_SHIFT; 06-06-2005 at 10:51 PM.
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post #7 of 9 (permalink) Old 06-06-2005, 10:57 PM Thread Starter
 
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Quote:
Originally Posted by PWR_SHIFT
Fellas, if I understood you correctly, what I think you're describing is clutch disc stick. Meaning, if the clutch sat engaged for some, even a relatively short, period of time, on some vehicles one side of the disc facing sticks to the flywheel surface, even though the pressure plate has moved off the disc. Usually it happens if there's excessive friction between the input shaft spline and the clutch disc hub (for whatever reason). Once you engage a gear with the shift lever the transmitted torque should jolt the system and shake the disc off the flywheel into its free position. Often this is the result of an overly tight fit between the disc hub and the input shaft spline and in addition possibly due to some driveline mislalignment. The tight fit is generally chosen to reduce the lash between the two parts and limit the driveline snatch during parking lot maneuvers and generally reduce driveline noises at low torque conditions. Still, should not be happening though.
How would this manifest itself? With the slight movement forward? or are you talking about the shifter not wanting to go into reverse/first?

Thanks for the info.
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post #8 of 9 (permalink) Old 06-06-2005, 10:58 PM Thread Starter
 
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Quote:
Originally Posted by Vanpaul
This is normal with manual transmissions. Though it is not as noticeable from one vehicle to another because of varying vehicle weights, rolling resistance, rotating mass and other things that I'm sure I am not thinking of. What is happening is that when the vehicle is running in neutral with the clutch out the clutch disc, transmission input shaft, upper shaft and sometimes a gear on the lower shaft are all spinning with the engine. When you depress the clutch all of these parts continue to spin for some time because of inertia. When you put it in gear the synchro tries to match the input speed to the 1st gear so as not to grind the teeth as it was designed to do. So all that inertia is transferred into a momentary surge of forward movement. When you take it back out of gear and try to duplicate it without cycling the clutch again, it does not happen because the previously mentioned parts were stopped the first time you put it in gear.
I thought the same thing but it just started doing this.
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post #9 of 9 (permalink) Old 06-07-2005, 09:46 AM
 
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It is normal.....
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