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Old 09-19-2016, 05:21 PM
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Quick trans question

Hey guys I've got a 2004 wj 4.0 w/ selec trac. I'm not used to auto transmissions so I'm just playing it safe here. When I'm on the highway I give just a little gas my rpms go up a couple hundred and then settle back down to around where it was before I gave it gas. Is this normal? I don't feel any jerking, hesitating, or shuddering. Thanks in advance!
- Kyle

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Old 09-20-2016, 05:22 AM
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Re: Quick trans question

Just a side note, I feel immediate response when the rpms go up. I feel like the transmission thinks about down shifting but changes it's mind. It also only happens when going from no throttle to just a little bit of throttle. If I hold the throttle steady and then slightly accelerate there's no rpm jump. I'm starting to think it's normal
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Old 09-20-2016, 06:58 AM
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Re: Quick trans question

When driving on the highway with a constant speed, the torque converter clutch (TCC) will be engaged and the torque converter is bypassed, making the connection engine to transmission a fixed one, reducing losses and heat buildup from a slipping converter. Normally, when accelerating just a bit, the TCC wil stay engaged and the rpm just increase gradually with the speed. When accelerating faster, the TCC will dis-engage, and the engine rpm will go up quickly. If this happens even with a very little extra throttle, it is not normal.
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Old 09-20-2016, 07:18 AM
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Re: Quick trans question

So I'm driving down the highway at a constant speed (foot staying on the throttle) and I give it gas, I don't see the rpms jump. I see them jump (only a couple hundred rpms) when I release the throttle (let's say to back off from the car in front of me) and then I very lightly accelerate.
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Old 09-20-2016, 11:33 PM
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Re: Quick trans question

This rpm jump must be the TCC disengaging. When it was a shift down, it would increase the rpm with around 500 rpm.
The TCC engaging/disengaging is controlled by the PCM. It uses for example TPS as an input to control the TCC solenoid. I would say that what you see is normal behaviour.
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Old 09-21-2016, 06:05 AM
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Re: Quick trans question

Thank you! My mind can rest easy now
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