Had to pull my toy hauler (travel trailer) to a local shop for a new awning today.
Straight road mostly gave me a good chance to see if I could hold 65 mph in 8th. The answer is simply, "No".
In tow-haul mode you only get 7th. Take it out and I had to get up to about 70 mph and the let-off the throttle to get into 8th. It would not hold any reasonable speed and would slow down under light throttle or jump back into 7th or even 6th.
My conclusion is just put the thing in tow haul and run it in 7th. It pulls fine with large profile trailers and saves the mental hassle of playing with the gearing and haul mode.
What's the length / weight of your travel trailer? Were you happy with the overall performance of the ed pulling that unit? How did it do compared to your previous rig and what was that?