March 2011, I completed my cross country trip towing a 5,000 pound trailer without any issues. We traveled from Virginia to Washington State, approximately 2,800 miles in six days. We encountered plenty of weather along the way, golf ball size hail, heavy rains, and a snow blizzard through the Oregon mountains. The snow had me very concerned with the fear of jack knifing, however, we made it through the mountains without a scratch, driving with a max speed of 20 - 30 MPH with DSC on the whole time. We arrived at our new home in the Seattle area around 3:00 PM, safe and sound. While unloading the X5 I heard a hissing sound from the rear right wheel, upon close inspection of the tire I noticed it had picked up a two inch screw along our lengthy drive and ultimately got a flat tire, which I repaired later on that day. Today as I write this, the X5 has 96K miles on the clock and it's still driving strong without any issues. Here's a pic of my rig at a truck rest stop:
Behind the trailer is my wife's 2010 BMW 335 Xi, "NOT" being towed.
I'm still contemplating whether or not to replace the X5 tranny fluid, any recommendations?