So, there has been a question in this forum in the past about towing capacity of 3-series.
I should have taken more pictures, but I recently moved from Klamath Falls, OR to Burlington, VT pulling an A-Hole (sic, U-Haul) 4x8 trailer. In short, almost no problems.
I had A-Hole install a hitch. I *ordered* the Class I hitch. They installed the Sport Hitch. I was, to put it gently, very pissed off. Not to mention a little worried. The Sport Hitch is installed by drilling five holes through the spare tire well and running bolts through the holes. Also, two holes and their attendant bolts are sunk through the bumper (@!$#^@#%^&$#^%&@^$&@$%^#%). And in case that was not clear enough, let me add @!#%@$^#$%&@$##$@%@$^@#%&$%^#!$^@#%&%$(*%&(%#^&#$^ &@%&#$^%&@$^*!!!!!!!!!!!!!!!
But, some friends just moved to the states from Denmark. They shared this humorous insight: almost all cars come with trailer hitches over there; this is because fuel and cars are so damned expensive, no family can afford a truck; the sign that your youthful, freewheeling days are over arrives when you buy a trailer to tote your stuff from the equivalent of Home Depot. Basically, they were of the opinion that these cars could handle this. "Of COURSE a BMW can tow a trailer!"
So, I weighed my car with the empty trailer (I threw away the piece of paper with all the figures on it)(@$!@$^%@!$%@$). I get my 4x8 trailer (I live rather leanly; this is pretty much the first time that I could not move all my stuff just in my car) and start loading it up. I balanced its load very carefully so as to not put more than 200 pounds on the hitch. I did this by standing on the tongue of the empty trailer (I weigh 180#), and having my better half measure the drop of the receiver relative to the ground. After loading a good amount of cargo, I measured the drop again. Repeat loading and measurement. After fully loading up the trailer, we went to the truck scales just up the road from my old house: ~1400 pounds of cargo.
The move went mostly flawlessly. Fuel mileage dropped from an average of ~25MPG highway to about 19 to 21MPG highway, depending on terrain. Interestingly, after I arrived and unloaded the trailer, I had to run some errands, pick up some groceries, get some 2x4s and plywood, etc. With the empty trailer, I got ~21MPG, leading me to believe that the primary issue with pulling the trailer was aerodynamic drag.
I wish I had taken a lot more pictures showing the whole get-up (the ones I did take don't really show much), but the long and short of it is that there are not too many issues with pulling a tralier. The car was squatted a bit from my aquarium in the backseat and tools in the trunk, but not nearly as much as carrying three of my buddies. With ~180 pounds on the tongue, there were no whipping issues in hard turns, although the trailer did tend to track to the outside if I took ramps 10 to 15MPH above their rated speed. And, with regards to my inquiry about transmissions, my tranny was making the noises before this move. All holy praise be to the engineers of BMW! (cue music: heavenly choirs of BMW engines singing near redline)