New F150 Ecoboost
 

Help! My brand new 2012 F150 Ecoboost (3.55 rear axle) sways at 60 mph when I test drove it pulling my 31ft Outback (9,600lb) pull-behind camper this a.m. Wanted to buy the 3.73 but dealership assured me the 3.55 was all I needed. Going back to them in the a.m.!!

I have discussed with the calibrators on the program and clearly the 373 is not required much less the higher ratio will limit the highway speed you can cruse at before seeing a decline in fuel economy. There is another advantage and that is you most likely don't have the maximum trailer tow mirrors which WILL NOT fit through a 9 ' garage door opening without being tipped in toward the cab.

It seems like there is a stability problem and I'm not sure a different ratio diff can solve this.