I have no doubt that an X5 35d can haul a 5,000 lb. rig, even with several hundred more pounds of load (gas, boating equipment, etc.). But I wouldn't recommend doing this on a regular basis for long runs at freeway speeds or mountains. IMO the issue is the automatic transmission, which is reported to be a fairly common weak point on X5s.

FWIW I'm one of only a handful of X5 (E53 and E70) owners on this forum who have posted that they fairly regularly haul near the upper limit of the X5's range i.e. an all up weight X5 + Trailer + load of 11,000 lbs. But I only do this on relatively short hauls e.g. typically less than an hour and never more than a few hours, one way.

Funf Dreisig

It's hard to argue for or against this from personal experience since it's hard for even BMW to know for sure but I've towed for many highway miles at 5,000+lbs with no transmission issues at all. The diesel is likely even better than my 2003 4.4i (torque is higher and transmission is better).

:iagree:We towed the same loads (e.g. approx 5,000 lbs.), in the same trailer, with our 2001 4.4i with NO transmission issues until it was totaled at just under 100,000 miles. But we never towed for more than 3 hours (one way) at freeway speeds*. And there have been a number of posts about transmission issues. So I can't recommend, based on my own experience, using an X5 for long distance, heavy duty towing.

OTOH I have always wondered if the reported transmission issues were more related to an aggressive driving style, than towing. :dunno:

Funf Dreisig

* FWIW this wasn't because we were afraid to use our X5 for towing runs longer than 3 hours; it was because that was the time/distance between our old house and the new house I was building :)

I don't think that driving distance on the highway is particularly related to wear caused by towing, if there is in fact any additional wear. Wear is usually related to high temperatures, which are tied more closely to start/stop cycles, and number of shifts (or the torque converter not being in lock up mode). If you are on the highway with the torque converter in lockup, there is no real cause of wear, towing or not.

There are lots of posts here by withidl relating to towing 8000+ pounds over the continental divide multiple times, in an early model 4.4. No transmission issues over the vehicle life.