We bought a 27' Flying Cloud last February that we tow with a 2001 Sub 4WD 1500
with a 5.3 V6 and the standard trailer towing option. Our Sub now has 123k+ miles.
We've been out close to 20 times so far. Although most of our trips have been up and down the coast, we have camped several times in the Sierra where we have traversed passes as high as 6000+ ft altitude. We regularly tow our AS, Iggy, up and down 6% grades; a couple were 9%.
On normal highways, in tow/haul mode there's almost no limit to speed, though we tend to travel between 55 and 65 mph. Iggy is an effortless tow, no sway and it seems as if it's on rails. Going up grades, we typically top out at 40 to 45 mph. The one time we were above 6000 ft, we crested at 30 mph. We pull over frequently to let faster moving vehicles pass. Seems to help keep frustrations in check and makes for a more pleasant journey.
I've had the Sub into our mechanic for a checkup and he says suspension and transmission look to be in good shape. BTW, I did install vented disks in the front to help prevent brake fade. They work great.
So here's my summary based on our first year:
The Sub 1500
handles towing Iggy just fine. We don't break speed limits going up extended grades, but after all ... we're on vacation ... Mileage tends to be between 10.5 and 11 mpg. Not bad on regular.
The Sub is very comfortable, quiet, and flexibly configured. I usually remove the third row seat to save load on the rear axle.
I think if we were spending a lot more time at high altitude, say like Wind River in WY, we'd pop for a new TV with a bigger motor. We plan to do some extensive travel a year or so out and that may be our motivation to getting something with more muscle.
However, for our use right now taking short-hop vacations, our Sub is great.
Hope this helps Enjoy the journey; life's a hoot!