are you able to get a snapshot of the values exactly when the car does it?

Test on a slippery surface like sand on gravel and see if you can reproduce the effect.

It’s actually pretty likely you are just getting wheel spin. Are you hitting the kickdown button at the limit of accelerator motion? If you are moseying around a curve in the typical situation of go under the bridge then left up the on ramp you’ll be in 4th. If you hit the kickdown the car will shift to second and the 3.0 can definitely break traction with old not awesome tires if there is just a little oily film from the cars before you.

I think you said you have x drive. Monitor the % to front. If the car is not putting enough torque to front, for sure, wheel spin.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)