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      09-22-2021, 01:11 PM   #1
erickonphoenix
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ZF-8 un-commanded downshift

First time this has happened.

Car in Sport plus, ZF-8 in manual mode, entering a slow corner under braking I downshifted to M4, M3, M2 then accelerated out of the corner. Shifted to M3 then to M4 when suddenly the transmission kicked down to M3 un-commanded pegging the car to redline. I hit the upshift again and it bumped back to M4.

I'm new to the ZF-8, I know the trans will upshift even in manual mode but I've never heard of one downshifting under load.

Now, one of my buddies (not a BMW person) speculated maybe I could have knocked the shifter out of manual mode. I didn't think to check when it happed but driving back I noticed the ZF-8 was back in auto mode and I don't remember changing it.
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      09-22-2021, 05:54 PM   #2
indyjoeshmo
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Does the intervention of traction or stability control revert the transmission to auto mode? I have a manual, so I'm just throwing out ideas.
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      09-23-2021, 11:04 AM   #3
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Is kickdown still active in the configuration you were using?
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      09-23-2021, 12:13 PM   #4
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Quote:
Originally Posted by indyjoeshmo View Post
Does the intervention of traction or stability control revert the transmission to auto mode? I have a manual, so I'm just throwing out ideas.
I had TC off so it's possible there some undetected slip and the ZF-8 reacted, but a downshift? Seems it would upshift or depending on the intelligence of the system reduce power to the rear wheels???

Quote:
Originally Posted by FaRKle! View Post
Is kickdown still active in the configuration you were using?
I really don't know. Kickdown usually happens when you go full throttle in too high a gear then the ZF-8 drops down to optimize the power band. The kickdown in this instance was abrupt and startling.
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      09-26-2021, 12:28 PM   #5
JoHnMuir
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I believe in the 328s the transmission is programmed to always have this behavior regardless of mode. I remember reading this was changed with the LCI and my 340i certainly does not exhibit this behavior. In Sport+ and manual mode (with shifter in sport mode) I can hit the rev limiter and be in whatever gear I want and the car won't do anything about it. The only thing it still does it auto select 1st gear when at a stop.
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      09-26-2021, 06:55 PM   #6
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My 440i only downshifts when I click the kickdown trigger in auto or S/A. But never in M/S
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