Towing with a tundra in the mountains

Put the tow/haul on and let it go. It will pull that weight all day long without issue. Don't be afraid of the high RPMs in the mountains, that's where the power is. Sounds loud but won't hurt anything. You may need to manually shift to a lower gear downhill if the engine braking isn't enough.

I've pulled some steep grades with my old Tundra and an 8k tt without issue. It pulled hard and could accelerate and keep speed with traffic easily. It did a much better job than my current Ram 2500.