I have pulled my 3400lb hobby car on a 2000lb 18' trailer with my X5 35D and experienced zero issues.

I had attempted the same pull with my newer (at the time) Silverado 1500. The transmission started slipping after three trips to the track.

The X5 pulls that 5400lbs effortlessly even up an ~8 to 10% grade. It's a pulling machine!