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2011 SS Automatic - Manually Downshifts on its own when stopping.

3004 Views 5 Replies 3 Participants Last post by  hypurone
Hey guys, got a problem I can't seem to find much about.....

The dealer talked to me like I was an idiot and inferred that I was accidently hitting the paddle shifter, which is not the case.

What’s happening is that from time to time, during deceleration generally, the car drops gears as if manually down-shifting, resulting in a surge forward. As this is while I’m trying to stop the car, this is a real problem and has nearly caused me to hit the car ahead of me at the stop. I have noticed twice that the display shows M2, which supports the manual down-shifting theory, but I am most definitely not doing it. One of these days an accident will occur, so I’m doing what I can to find the problem and get it resolved. The dealership wants to drive it, but as it’s about a one in 500 occurrence (thereabouts) it’d be pointless to do this. I asked them to check the computer, they report no issues logged.

Any ideas?


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Yes, it's in drive, not S. Paddles are not engaging either intentionally nor (from what I can tell) through physical malfunction. It's such a rare thing that I can't force. When I manually downshift it shifts down with no surge forward, so I really don't think it's a normal downshift of any kind. The forward lurch just doesn't make sense.

Not clear on what's going on with your cornering issue. I don't have that problem to my knowledge. This normally happens in normal driving, decelerating for traffic or lights, so at low-ish speeds, on straight roads.

Thanks for your thoughts!!

The autos do what is called "rev matching" on the downshifts when in M or S mode and may be what you are feeling when it does its own inadvertent downshifting. Still, it is def not normal for it to do it on its own UNLESS it is in Sport mode. I would ask the dealer if there are any updated calibrations for all the control units on the car (ECM TCM BCM). They are usually applied together, at least for the ECM and TCM....

If they are no updates, remove the positive battery cable and let it sit overnight to drain residual power from the control units. This is overkill but will ensure complete reset. The trans is an "adaptive" unit and the TCM "learns" shifting patterns and stores them. It may have stored an incorrect shift procedure or simply botched it when storing....
That makes sense, Chuck.
Thanks for the suggestion.
Sure,np. Let us know what happens..
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