F30POST
F30POST
2012-2015 BMW 3-Series and 4-Series Forum
BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read
BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > Tracking / Racing / Autocrossing > ZF-8 un-commanded downshift
ARMA SPEED
Post Reply
 
Thread Tools Search this Thread
      09-22-2021, 01:11 PM   #1
erickonphoenix
Lieutenant
erickonphoenix's Avatar
1709
Rep
532
Posts

Drives: 2014 Gray 328xi Touring
Join Date: Jun 2015
Location: Houston TX

iTrader: (0)

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.
__________________
Appreciate 1
      09-22-2021, 05:54 PM   #2
indyjoeshmo
Private
32
Rep
70
Posts

Drives: F30 335i Sedan
Join Date: Dec 2019
Location: Indianapolis

iTrader: (0)

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.
Appreciate 1
      09-23-2021, 11:04 AM   #3
FaRKle!
Brigadier General
3996
Rep
3,533
Posts

Drives: 328d Wagon, M2 Comp, i4 eD35
Join Date: Sep 2016
Location: Bay Area, CA

iTrader: (4)

Garage List
Is kickdown still active in the configuration you were using?
__________________
-328d Wagon Build Log (with helpful reference links)
-My YouTube Channel for some of the best DIYs and in depth information

Please don't PM me for suspension recommendations unless interested in paid private consultations.
Appreciate 1
      09-23-2021, 12:13 PM   #4
erickonphoenix
Lieutenant
erickonphoenix's Avatar
1709
Rep
532
Posts

Drives: 2014 Gray 328xi Touring
Join Date: Jun 2015
Location: Houston TX

iTrader: (0)

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.
__________________
Appreciate 1
      09-26-2021, 12:28 PM   #5
JoHnMuir
Private First Class
70
Rep
131
Posts

Drives: BMW 340i
Join Date: Jan 2021
Location: NJ

iTrader: (0)

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.
Appreciate 2
      09-26-2021, 06:55 PM   #6
alexander7599
Alexander Hartunian
alexander7599's Avatar
United_States
58
Rep
95
Posts

Drives: 2018 BMW 440i
Join Date: Sep 2018
Location: Napa, CA

iTrader: (0)

Garage List
2018 BMW 440i  [0.00]
My 440i only downshifts when I click the kickdown trigger in auto or S/A. But never in M/S
__________________
2018 F32 440i - Black Sapphire Metallic - KW Suspensions V1 | VRP Intake | VRSF Catless Downpipe | Dorch Stage 2 HPFP | MHD OTS Stage 2 E40
Appreciate 2
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 08:56 AM.




f30post
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST