I just had this issue with our F15, not that it correlates to your E70, but it's a data point. We had ~45k mile tires on it and were experiencing a tugging/hesitation/misfire sensation at different times but easily reproducible around 40mph. Replaced with a new set of rubber about a week ago (250+ miles) and have not had it happen again. I was just about to do the transfer case fluid and reset adaptations (still am, truck has 91k miles) thinking that may help. Seems the Xfer cases are very sensitive to tire diameter differences.

Other thing to check as it's quick... pull your Xfer case actuator motor and look at the gear. I'd figure you would get other symptoms with this failure, but it's worth a look given the small time investment.

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)