[475bhp m135i]

Hi guys

I have a m135i running 475bhp

I have just changed the clutch and flywheel and just got the car back

Now the drive train issue is coming back up coursing a miss fire and throwing a clutch slip fault

How ever this only ever happens when I’m in 6th gear under 60 and plant my foot

But if I drove the car like I stole it and dropped the gears down this doesn’t happen and dose not throw up the fault

I have rest all adaptions cleared the codes and it’s still happening

For obvious reasons I don’t want to keep driving it like a knob lol and it’s highly annoying

Please if anyone has had the same issues please let me know what it would be

I’m also taking it back to the garage to get them to check everything they done

[Keltek340i]

Now that sounds super frustrating, especially right after paying for a clutch + flywheel job.

What you're describing is a classic "low rpm, high load" slip detection on the N55/B58 platform in the M135i.

What's probably happening
*6th gear under 60mph + full throttle = massive load at low RPM*
That's the worst case scenario for a clutch. The DME sees engine RPM rising faster than wheel speed and thinks "clutch slip". It then cuts torque, throws the clutch slip fault, and often pulls timing which feels like a misfire.

What to tell the garage to check
- *What clutch kit did they actually fit?* Part number + torque rating. For 475bhp you want something like Sachs Performance, Helix, or MFactory rated 650Nm+.
- *Was the flywheel OEM DMF or SMF conversion?* If DMF, was it new and correct for N55?
- *Run ISTA clutch teach-in procedure* and check clutch adaptation values
- *Log data*: RPM, wheel speed, boost, ignition timing in 6th at 50mph WOT. You'll see RPM jump vs speed if it's slipping.
- *Check for fault codes beyond clutch slip*: 30CF, 30D0 misfires, 420351 clutch torque monitoring



For now: avoid WOT below 2500rpm in 6th. Drop a gear. It sucks but it saves the clutch and gearbox while you sort it.

Did they tell you what brand clutch/flywheel they fitted? And is yours N55 or B58 M135i? That changes what clutches actually hold 475bhp reliably.

Hope they sort it when you take it back. Let me know what they find and I'll help you figure out next steps 👍