Is is alright to coast with the truch in "N" or should I keep it in drive. When going down a long hill the truck (empty) wants to "slow down" I would like it to maintain it's speed at the least. Maybe this is how the Allison is supposed to work but empty?

The Allison grade-braking does work in both regular and tow/haul mode, it's just MUCH more pronounced in tow/haul. What you're describing sounds like normal behavior for this drivetrain. You could use the cruise control to keep your speed constant in this situation, unless the downhill grade is full of severe curves, of course.

Just step on that little pedal clear to the right, it cant slow down if you got your foot in it!

):h Thanks Dave!! Trying to get better gas mileage though!! By the way, thank you for serving our country!