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Shifting Gear 1->2 as RPM decreases

Old 07-14-2018, 04:50 PM
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Fantality4
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Shifting Gear 1->2 as RPM decreases

Hello,

So from time to time I would get obnoxious rattles when shifting from gear 1 to gear 2. I didn't know what was causing this and I didn't know how to recreate the phenomenon. It simply happened on average of once or twice during each of my driving sessions. I thought something was wrong with my car.

I finally figured it out today. I was able to replicate the issue. The rattling happens when the RPM is decreasing during the shifting from gear 1 to gear 2. So, I have to either shift 1->2 at the exact climax of the rpm or when the rpm is increasing.

Is this the only cause of the rattle? I don't know. Maybe others can share what they've discovered.

My car is the '13 G37S Coupe 6MT.

Last edited by Fantality4; 07-14-2018 at 06:13 PM.
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Old 07-14-2018, 05:59 PM
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slartibartfast
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Rattle? As in two loose pieces of metal hitting other? Or detonation?
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Old 07-14-2018, 06:12 PM
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Fantality4
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Originally Posted by slartibartfast View Post
Rattle? As in two loose pieces of metal hitting other? Or detonation?
Like a lot of things on the under-carriage shaking in an unnatural way. This is for the coupe. Specifically the Sport version. I don't know if it's only applicable to Sport or the coupes in general. I made a recording but the recording hides the rattling noise with all the other background noises.
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Old 07-14-2018, 11:15 PM
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slartibartfast
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The only rattling reports on the G that I've seen deal primarily with loose cat heat shields or detonation from running 87 octane gas. It's strange you report it only during the 1-2 shift.
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Old 07-15-2018, 01:59 AM
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Fantality4
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Well, this is really easy to recreate. I've done it on two G37S 6MT's now. In 1st gear, accelerate to like 3k RPM, and let it idle for a second or two until the RPM starts decreasing before shifting into 2nd. Then you'll hear it.
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Old 07-15-2018, 06:43 AM
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If I'm in first decelerating and hit the clutch i get a rattling too. My car has always done it, never really bothered me. I just make sure i overlap just slightly with the gas pedal when going to a stop in first. I also need to replace every mount on my car so i assume that might have something to do with it.
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Old 07-15-2018, 09:22 AM
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More than likely you are hearing the dual mass flywheel rattle.
This is normal for our cars and nothing to worry about.
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