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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > N55 Turbo Engine / Drivetrain / Exhaust Modifications > Stutter from ZF 8 speed
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      02-08-2020, 02:58 PM   #1
Fudz
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Stutter from ZF 8 speed

I recently flashed BM3 93 RON stage 1 and the BM£ TCU flash. The car is a completely stock 435i with 60k. I haven't really driven it hard or much today but noticed a substantial gain in performance.

I have noticed on the motorway though if i pull out to accelerate in 8th in sport mode and feed in the throttle to full as the torque builds - as seen on the performance dials on Idrive, I get a double shudder from what feels like transmission. It's feels like a cog is slipping etc under torque. Is this a common/normal thing, something to be avoided by downshifting etc or a possible sign of an issue.

I didn't think a stage 1 map would push the limits of the transmission especially with a flash to improve torque capacity etc.

Is there anyway to log the transmission


Any help is appreciated
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      02-09-2020, 01:31 PM   #2
thejeremyman9
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No, not normal.

You can't really "log the transmission" but you should be able to capture a log of when it happens so we can see the behavior of logged parameters when the issue occurs.

I would recommend removing the trans flash but keeping the tune to see if it still happens.
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      02-10-2020, 10:34 AM   #3
BuefordTjustice
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60k mi, have you replaced the stock plugs yet? Even without the tune the plugs are due to be replaced. Having the tune with plugs that aren't efficient could cause the bucking you're describing.
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      02-10-2020, 11:41 AM   #4
Pray for Mojo
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The tune isn't 93 RON, it's 93 AKI, you need 98 RON to run that tune.
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      02-10-2020, 01:08 PM   #5
Fudz
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I'm using 97 RON here in the UK, Plugs also done 2k ago at factory gap
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      02-10-2020, 01:16 PM   #6
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You should do a log in 3rd or 4th gear to redline, that way you can eliminate the possibility you are having HPFP crash/engine stutter vs transmission slip.
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      02-10-2020, 02:43 PM   #7
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I was reading into the hpfp crash as it is common on the V7 maps, although I am not sure it would be as bad on a stage 1 map but it does sound very similar.


When the weather turns for the better here I am gonna grab a log
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