While driving though South Dakota's Black Hills carrying around 2000# worth of slide in camper and the cruise control set on about 65 mph, the engine would occasionally run up to 4250 rpm to maintain the speed. Does that in any way stress the engine or transmission too much?

 

No, they are built to do that all day everyday with 5X that load.

 

what kind of mileage are you getting with the 3.73s?

 

If my memory is correct, max torque is 3750 rpm's, and max h.p. is at 5,000 rpm's.

I just ran my '08 CC 4WD 5.4/3.73 over 5,000 miles across the country, WA state to TN and back. On the trip back I was towing a 7,000+ pound enclosed trailer (aero drag as well), and had a fully loaded truck (close to 2,000 pounds in the cab/bed) and it pulled some rpm's, but did great. I set the cruise and it just went. I usually ran 5 mph over the speed limit, up to 80 mph in NE/WY. I sometimes pulled near 5,000 rpm's on long grades, but I never slowed to less than 60 mph, and then only 2-3 times, on the steepest grades in the whole trip - I spent many hours above 3,000 rpm's. None of my gauges even moved from their normal marks - these trucks were built to work.

The chassis/brakes and TS transmission are also great. It's a fantastic tow rig - even when fitted with modest power...

 

get yourself a nice muffler and you'll love running that motor at that RPM in fact..

 

dfboothe - On this trip the truck got right at 12mpg averaged for the entire trip. That was a 900 mile trip from Laramie through the Hills and return.