Erratic shifting - is it the computer? Trans "feels" fine. - Chevy Impala Forums
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post #1 of (permalink) Old 12-30-2016, 06:10 PM Thread Starter
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Erratic shifting - is it the computer? Trans "feels" fine.

Not sure if this should go in Engine or Drivetrain so figured I'd ask in the general discussion.

My 8th gen is weird when it comes to shifts - but it doesn't seem to be the transmission slipping or anything, more like shift points are weird? If I give moderate acceleration, the vehicle tends to not shift into the next gear for a few seconds after I return to "normal" throttle position to maintain speed. Then, it seems to upshift much easier than normal for quite some time, even without much acceleration at all. It has erratic shifting for quite some time, even after turning the vehicle off overnight. I haven't unhooked the battery since I've installed my stereo (don't want to lose my settings), but it even did it while I was in the process of doing that and left my battery off overnight a few times.

Is there a way to fix this? The transmission feels solid, the shifts feel good, they just don't happen anywhere close to where they should and are erratic after moderate/heavy acceleration. Hell, there are times where it'll go into 3rd or 4th and just sit at 3k RPM for no reason as I'm driving normally, then it'll shift into the next gear or two to get down to cruising RPMs. If I have to buy a tune to fix this, then I'll start saving, because I'm getting tired of it!

Thanks for any insight, and sorry for the wall of text!


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post #2 of (permalink) Old 12-30-2016, 10:02 PM
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Have you checked for any codes (even if CEL isn't lit)? Strange issue... How many miles? Really hard to troubleshoot without any codes though - issue could be anywhere. So the car hasn't always shifted like this, correct?

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post #3 of (permalink) Old 12-31-2016, 09:12 AM
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Are you sure you're just not experiencing the '13 Impala's drive-by-wire and funky eng./trans. tuning and shift points?
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post #4 of (permalink) Old 12-31-2016, 12:09 PM Thread Starter
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@jtrosky - No CEL. 57k miles. It's shifted like this for a while, but maybe I'm coming more aware to it now that I've got a second vehicle that shifts like butter... haha.
@sheila - I could be - and just wanted to make sure it was either "normal" or nothing wrong, and if it could be fixed with a tune and new shift points, then that would be the next direction I go?


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post #5 of (permalink) Old 01-01-2017, 04:49 AM
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Originally Posted by carbon_x View Post
@jtrosky - No CEL. 57k miles. It's shifted like this for a while, but maybe I'm coming more aware to it now that I've got a second vehicle that shifts like butter... haha.
@sheila - I could be - and just wanted to make sure it was either "normal" or nothing wrong, and if it could be fixed with a tune and new shift points, then that would be the next direction I go?
No CEL, but have you actually checked for codes with a scanner? Sometimes, there can be codes stored on the computer without triggering the CEL.

Sheila may be right - maybe it's just the way these trans are. For example, if you really give the car a lot of throttle on the highway and it downshifts, you sometimes almost have to let off the gas completely before it will upshift. That is normal - it's how the trans shiftpoints are tuned. I've confirmed that it's supposed to do that via HPTuners. I was going to change it so that it upshifted sooner under those situations, without letting up on the throttle so much, but I figured it might be too hard on the trans, which is why it's like that to begin with.

I'd say that if it's always shifted like that, then it's probably normal. But if the shifting feel has changed dramatically since you first got the car, then maybe it really is an issue.

Under light throttle, upshifts should be pretty quick and "consistent". But after letting up a little after heavy throttle, the trans definitely feels "strange" - like I said, sometimes you almost have to let off the throttle completely before it will upshift.

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post #6 of (permalink) Old 01-01-2017, 09:22 AM
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Quote:
Originally Posted by carbon_x View Post
@jtrosky - No CEL. 57k miles. It's shifted like this for a while, but maybe I'm coming more aware to it now that I've got a second vehicle that shifts like butter... haha.
@sheila - I could be - and just wanted to make sure it was either "normal" or nothing wrong, and if it could be fixed with a tune and new shift points, then that would be the next direction I go?
Probably not a thing wrong lmfao. It's these impala stock tunes and torque management that makes the shifting sloppy and slow. Meant for a grand pa. Need way to much TP% to even change gears. Tune got rid all of these sloppy problems for me.
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post #7 of (permalink) Old 01-01-2017, 04:04 PM
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The symptoms you're experiencing are most likely normal. After heavy throttle the car tends to hang in the lower gears longer than feels necessary. I've had several automatics behave this way. It could be like they said to preserve the trans, but it could also be that the vehicle thinks you may get back on the throttle? I'm not sure, but either way, my trans on my '13 behaves the same way. It can be irritating when just merging on the expressway then wanting to cruise, but it's kinda nice when doing some spirited driving on some back roads.
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post #8 of (permalink) Old 01-04-2017, 10:28 PM Thread Starter
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Thank you all for the feedback. It seems that the feeling I'm getting is normal - and I'm gonna have to look into a tune, then. I'm just not liking the way the stock tune works anymore, haha!

Thanks again for the feedback!!!


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