Car jerks when putting in first

Synchros shot? Weird noises while shifting? Not sure what needs to be replaced?
mande110
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Car jerks when putting in first

Postby mande110 » Sat Aug 25, 2012 2:40 am

I recently noticed a very light jerk when i put the car into first gear from a complete stop. I completely depress the clutch and put into first and the car gives a slight thump, which kind of feels like the clutch is grabbing ever so slightly. What is strange is that it does this but once i pull it out of first and then put it into first again it doesn't jerk. It only happens after I come to a complete stop and the first time i engage first gear during that stop. The car is completely stock with 22XX miles. Maybe im just crazy lol

Roger
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Re: Car jerks when putting in first

Postby Roger » Sat Aug 25, 2012 2:51 am

Does the RPM change a bit when you get the jerk? Do you feel the whole car kind of move or is it more of a clunk similar to when you put it in reverse?

mande110
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Re: Car jerks when putting in first

Postby mande110 » Sat Aug 25, 2012 2:58 am

I'll have to double check on the rpm. If you wouldn't mind could you explain to me the difference between the two situation. My car does really jerk when going into reverse, my reverse is a combination of 1st and 3rd with an reverse idler gear.

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Re: Car jerks when putting in first

Postby Rope-Pusher » Sat Aug 25, 2012 3:11 pm

If you were idling with the trans in Neutral and the clutch engaged (Oh, this is so soon, I wasn't expecting,....Yes, Yes I'll marry you!) the clutch and the transmission input shaft would be spinning at idle speed. If you then disengaged the clutch (It's off? What did I say? What could I have done differently?), they would still be revolving at idle speed for a short while, until it coasted down to a stop, If, while they were coasting down, you shifted the transmission into a gear, the synchronizer for that gear would bring the input shaft to a stop, since that is the input shaft speed associated with zero output speed for any and all the gear ratios in the silvebox. While this rotating inertia was being brought to a halt, there would be a reaction against the transmission/powertrain mounts. This is often perceptible as a little jerk, not to be confused with Tony.
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Re: Car jerks when putting in first

Postby theholycow » Sat Aug 25, 2012 5:52 pm

Assuming that the input shaft is still spinning:

You can wait for the input shaft to stop spinning, just by sitting there with the clutch pedal down.

You can try stopping the input shaft with another gear's synchronizer. Pretend like you're going to shift into 2nd, but before it lets you into 2nd abort that maneuver and shift to 1st instead.

You can avoid the entire situation by leaving it in gear as you come to a stop, just step on the clutch pedal and come to a stop with the transmission still in gear. It doesn't matter which gear. Once at a complete stop, you should be able to shift to 1st immediately and smoothly.

If the input shaft never stops while the clutch pedal is fully depressed, your clutch release system may not be functioning perfectly or your clutch may not be sliding smoothly on the input shaft (and that's regurgitated advice originally provided by Rope-Pusher, so thank him, not me).
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mande110
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Re: Car jerks when putting in first

Postby mande110 » Sat Aug 25, 2012 7:46 pm

Thank you for all your help im going to try the leaving it in gear when coming to a stop later today. I think it took me this long to notice it due to holding the brakes when putting the car into first. Once again thank you all! :D I thought my car was broken so im relieved!

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Re: Car jerks when putting in first

Postby IMBoring25 » Sun Aug 26, 2012 12:25 pm

Another approach is to leave the clutch in during the stopping process. Even if you take the transmission out of gear this should usually give the input shaft and clutch time to spin down before the shift into first, unless you're one to brake like you're on a race track.

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Re: Car jerks when putting in first

Postby Tups » Sun Aug 26, 2012 12:31 pm

I wonder why I read the topic as "girl jerks when putting in first"...
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theholycow
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Re: Car jerks when putting in first

Postby theholycow » Mon Aug 27, 2012 6:39 am

IMBoring25 wrote:Another approach is to leave the clutch in during the stopping process. Even if you take the transmission out of gear this should usually give the input shaft and clutch time to spin down before the shift into first, unless you're one to brake like you're on a race track.

Time doesn't matter. When you do that, you can be 100% sure the clutch is stopped as soon as the car is stopped, as the clutch is connected by the gears to the wheels.
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Re: Car jerks when putting in first

Postby AHTOXA » Mon Aug 27, 2012 8:57 pm

If it jerks, try putting it in last.
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Re: Car jerks when putting in first

Postby Squint » Thu Aug 30, 2012 11:40 am

AHTOXA wrote:If it jerks, try putting it in last.

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