I had my trans serviced (87k miles) because of a hard 3-2 shift coming to a stop. Also replaced the filter, pan and that rubber gasket that goes to the valve body, following a thread on the E53 forum. World of difference, even though the fluid appeared fine.

The key probably needs a battery. I don't think these charge from the car. One of mine needed a battery so I replaced both at the same time. No re-coding needed (for me).

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Mike

2005 e53 X5 4.8is 169k miles
2018 f90 M5
2018 Volvo XC60