Need more data!!!
What do you mean by "highway speed"? How fast are you trying to go when this happens??
Headwind..... How much of a headwind????
It is a Pentastar V6. Torque is 260 ft.lb @ 4400 rpm.
Transmission is a Chrysler 62TE. 5 gear is 1:1 direct. 6 gear is .69:1.
The “fourth prime” gear, similar to the Chrysler 45RFE/545RFE’s “prime” gears, was used for kickdowns only. When moving from a lower speed, the transmission used the standard fourth gear; but, once in a higher gear, the transmission could kick down to “fourth prime” instead of fourth, to make the shift feel smoother.