DSAviate:

'04 and later have more capacity only in the automatic 3.0. I wouldn't call it beefier, everything else is the same except the transmission, at least with respect to towing capacity.

I'm with you on the manual transmission, and the M54. Look at my signature. Brilliant engine. Since you understand that you won't be winning drag races towing down the on-ramp, you will be fine with the 3.0. And yes, they are happy to rev.

I don't think the transmissions are a weak point. There are reported failures at higher mileages, but there is no obvious correlation to trailer towing. Many of the failures include things like sensors and actuators, not failures related to heat dissipation.

Suggest you do a search on a poster here called withidl. He towed 8300 lbs of Airstream with his 4.4, for tens of thousands of miles. Good reference as to the vehicle's capacity. There are also other posts about towing larger loads with the 3.0

Good luck

Jeff

__________________
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue