X5 Shaking at Mid to High Speeds!

[Bavarian]

Today I found out a new problem with the X5. Just 2 days ago, it died of its battery. Looks like I'll see my rep every other day now with these service issues.

Today I was driving on the highway. I was going at 110km/h (about 65MPH). I had already driven 25km (15M) so far and everything was fine.

All of a sudden, my steering wheel started shaking and shuddering. It was a side to side motion at first. The car still went where I wanted it, but the steering wheel vibrated left and right, so I had to hold on tight.

At first I thought there was something with the road. I switched lanes, and the vibrating continued. I slowed down to 80km/h (50MPH) by letting off the gas and during the decelleration, the shaking got even worse. The whole car was violently vibrating and shaking. At 80km/h the shaking decreased, and it stopped once I reached 60km/h (38MPH). If I went above this speed, the car shook violently. It didn't matter if I was giving gas, coasting or braking - it shook.

I pulled over and checked the tires, rims and suspension for obvious damage and found nothing. The engine worked perfectly, as did everything else in the car.

I drove for another 40km (25M) at 60km/h with my hazards on. Then I tried accelerating again. It worked! I could reach 150km/h, and still no shaking. Drove at 120km/h for about 30km, and then the shaking returned again suddenly.

This time, I also noticed a constant jurking motion back and forth, too. This makes me think the clutch is slipping or something is up with the differential for the AWD. It was weird. I would give gas, and the engine would rev up 1000RPM, yet I could feel almost no acceleration. It's like the clutch wasn't engaged!

I'm bringing the car to the dealer first thing Monday morning. Any ideas?