I may have the chance to try a smarty on a trip (1500-2000 miles) and wondered what setting would be recommended for hauling a 9000lb 5er with a 2006, slt, quadcab, auto with cia and 4 inch performance exhaust.
Thoughts I am after effeciency and not to blow up my motor or tranny.

 

1 or 3. 3 is max for a stock trans.

 

I tow on # 1. My trailer is #16,000 so I wouldn't think you would have any problems.