I have the same rear diff gear ratuo. Depends on the grade thar you are driving throuh. My truck does ocassionally go into 4th gear on the highway on a steeper grade. If you are going through big hills or pushing through a lot of wind I would think you are OK. On the highway I tow in "D" not "M". I lock out 6th if I a off the expressway or if there are hills.
If you are brand new and towing your shift points could still be a little off.
If you are brand new and towing your shift points could still be a little off.