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Jerking when shifting
Do your guys cars jerk a bit when shifting from 1-2 and 2-3? I think it's normal for manual trans cars and a lot depends on the driver but it seems like whether I completely take my foot off the gas when releasing the clutch or eve so slightly touch the gas as the clutch is coming out the car jerks. It's very rare that I make a perfectly smooth shift. Is this just part of the charm of a 911 SC or does an adjustment need to be made? I replaced the trans and engine mounts with factory rubber type. Do harder mounts make this jerkiness worse or better?
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10-28-2017, 07:15 AM
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Reiver
Join Date: Nov 2011
Posts: 57,473
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No, mine does not. Slipping clutch that grabs?
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10-28-2017, 08:31 AM
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Location: Grapevine, TX
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It sounds to me like an RPM miss match when you are letting the clutch up. That RPM are you shifting at, and how far do you let the ramps dip during the shift? If the RPMs drop down and the have to be forced back up by the engaging clutch it will cause cars buck as the engine is forced back up to match the transmission input speed. Next time you are out driving pick a shift RPM 2-3 (say for instance 3000) and note what speed you are at before the shift. Now shift to 3rd and bring the car back to that speed and note what RPM you have for 3rd gear (guessing around 2200). Now practice shifting at your chosen shift point and modulate the throttle so that the RPM match the next gears RPM for the given speed.
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10-28-2017, 09:34 AM
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The jerk you are feeling is from engaging the clutch under power. You need to change your shifting timing. Don't get back on the gas until you've released the clutch all they way.
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10-28-2017, 10:03 AM
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Quote:
Ok so foot completely off the gas when releasing clutch? When I do that you get a much more dramatic mismatch like previous responder said. Engine rpm drops significantly and then when engaging clutch your feeling the big change in rpm as the clutch comes together with the now low engine rpm. That's why I tend to have ever so slightly throttle to keep engine rpm closer to clutch rpm for reengagement. But all said and done it seems like I'm jerking one way or another. Occasional smooth shift. This is a very hard thing to describe in words obviously. But I'm just trying to figure out if it's just me or if there's some extra play somewhere in the drive line that needs to be addressed. Sent from my iPad using Tapatalk |
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10-28-2017, 10:16 AM
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Obviously, I'm not in the car with you. But I'm 99% sure it's your technique. If the RPMs are falling too far when you shift, you're probably not reengaging the clutch quickly enough.
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10-28-2017, 11:02 AM
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Location: Socal
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Try blipping the throttle between changes and see what effect it has ..
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10-28-2017, 11:04 AM
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It seems like once the clutch is fully engaged and I hit the gas I get like 2 jerks and then once the RPM is passing like 3k it's just hammering down and the car is off to the races. But like right upon clutch engaging the engine and I hit the gas it jerks on the low end of the rpm and then it's off to the races.
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10-28-2017, 11:54 AM
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I could swear the car jerks after switching to 2nd and 3rd all on its own but once I get the power on it's smooth and the backend squats down and the car rips. It's just right after the gear change I get a little herky jerk
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10-28-2017, 11:56 AM
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I think it's play in the mounts of something. The weight of the engine and trans lunging back and forth between gear shifts or something
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10-28-2017, 12:00 PM
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If it was play in the mounts or something similar to that, it would happen simply from getting on and off the throttle in a gear. You wouldn't have to change gears to have the problem.
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10-28-2017, 12:37 PM
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I'm thinking the revs haven't had a chance to drop enough for the next gear (when shifting up). My SC was like this at one time and I plugged one of the CIS components and the revs would drop the split second I took my foot off the gas.
Last edited by Bill Douglas; 10-28-2017 at 02:36 PM.. |
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10-28-2017, 12:50 PM
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Ok well thanks for the input fellas. I guess until I get a chance to drive another SC I'll just have to take responsibility ha.
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10-28-2017, 01:01 PM
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1982 Porsche 911 SC
