I would determine first that the ABS module is at fault, and not one of the speed sensors or a faulty connector... The tranny will hunt for a gear when it is getting incorrect (not plausible), or missing speed signal...at the end of the day, it may go into limp mode... and drag the engine into limp mode...

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E53 X5 4.6iS
147K mi - Sold May 2013
Tireprints left in:
USA, Nicaragua, Costa Rica, Panama, Russia

E53 X5 4.8iS built 2005-10-17
66200 mi - June 2012
96000 mi - June 2013
112000 mi - June 2014
OEM fire extinguisher
OE first aid kit
OE tow hitch
OE TV module
OE aspheric mirror
K&N air filter
black/white badges
rear camera
4-channel video recorder

Here is the list of things I have done to the X