Rpm bounce - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
Problems and Service Talk about any mechanical problems you are having

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post #1 of 12 (permalink) Old 06-13-2012, 04:35 PM Thread Starter
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Rpm bounce

I have an 09 cobalt ls with an automatic transmission. The problem I've been having for quite some time is at 35-42 mph the car shifts from 3rd to 4th to 3rd to 4th and the rpms bounce until I speed up and it stays in 4th. What can I do to fix this? I've read other posts and ppl had similar problems and changed fuel filter, air filter and cleaned the throttle body. Will this help?

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post #2 of 12 (permalink) Old 06-13-2012, 06:11 PM
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I think there is a silent recall bulletin. Check with your dealer or Sarah. They have to reflash your TCM with different shift points and hysteresis data.

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post #3 of 12 (permalink) Old 06-13-2012, 06:35 PM
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If you like, I am also able to check into recall information on your vehicle. Please send me the last 8 digits of your VIN (I see that you're a new member, and I believe that you would be unable to send a private message at this point; however, I have sent you my email address that I can be reached at) and I'll get you more information.

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post #4 of 12 (permalink) Old 06-13-2012, 07:15 PM
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Sarah will a silent recall or service bulletin show up on your list when you enter a VIN or just the actual recalls.

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post #5 of 12 (permalink) Old 06-14-2012, 10:18 AM Thread Starter
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I replaced the air filter and cleaned the throttle body and so far my car hasn't been doing it anymore. It stays in 4th. I'll see how it drives for now.

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post #6 of 12 (permalink) Old 06-14-2012, 01:40 PM
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Coby7,

I can see recalls, but wouldn't be able to see a TSB.

09LS,
Glad that you have things taken care of! Hope that the air filter replacement/throttle body cleaning combo takes care of it!

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post #7 of 12 (permalink) Old 06-14-2012, 03:40 PM
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This is the bulletin I was thinking of...but it might not apply to yours.

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Certain 2007-09 Chevrolet Cobalt vehicles, equipped with a 4T45E (RPO MN5) automatic transmission, may have had the transmission control module reprogrammed with calibrations that do not provide desired transmission torque converter clutch and shift performance.

Correction
Dealers are to reprogram the Transmission Control Module (TCM).

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post #8 of 12 (permalink) Old 06-14-2012, 04:06 PM Thread Starter
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Had to reread that a few times... I haven't had anyone work on the trany if that's what you mean, like someone didn't set it up correctly when they worked on it?

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post #9 of 12 (permalink) Old 06-14-2012, 04:43 PM
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No, this bulletin is for transmission that were misprogrammed at the transmission factory.

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post #10 of 12 (permalink) Old 06-14-2012, 05:25 PM Thread Starter
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How can I find out if that's the problem? I hooked up a code reader to it b4 I cleaned it up and it didn't have any codes.

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