Quote:
Originally Posted by cyam
So I had a similar although much more minor version of this issue.
As it changed gear at WOT from 3rd to 4th I would get a shudder. And as it hit redline before that gear change, it seemed like it was hitting the rev limiter and bouncing around first, then change with a shudder.
So I found out it was my tune that was the issue. The tune was fudging the torque values being sent to the TCU. Instead of reporting (e.g.) 600nm to the TCU, it was down-scaling them and just saying "500nm" - because the gearbox has torque limits at around 550nm. So the tuner, to avoid limiting the tune to 550nm, simply got the DME to lie to the TCU about the actual torque being sent.
So this prevents the gearbox sending a torque reduction request to the DME.
Problem is that the gearbox thinks its only getting 500nm and adjusts line pressures etc for 500nm, but it was getting 600nm. So it starts to cause the gearbox to slip, shudder etc.
When I figured all this out, I ditched my tune and switched to MHD - which does not do this, and my gearbox has not had this issue at all since.
That's what happened to me. Your tune may not be doing this and its something else entirely. But maybe this can point you in the right direction.
To me it sounds like the gearbox is not using enough line pressure for the torque its been sent. Could this be a possibility?
Also remember that the gearbox does reduce torque at the gear-change to smooth out the change and reduce wear. There are one of three ways it can ask the DME to do this. Could it be that the torque reduction at gear change settings are [...]
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Hey man. Thanks for the update.
Yeah I somehow figured out the same thing but in a much less nicer way lol.
I just kept reflating my car and realized the higher stage tune I use, the worse it is.
Stage 0 MHD and xhp gave me the best results and the car has a very mild thud on gear changes.
Another thing I found out was the transfer case code. It apparently means you need to replace your transfer case 😵‍💫
According to bmwfault.codes site.
They updated it recently to give more info on that code.