Use the tow mode and let the transmission do the work. You may get up to 4000-5000 RPM but that is normal going down hills, the Triton engine is made for it. If you start picking up too much speed, use your brakes in time periods to slow down. I have been through some pretty steep mountains (5-6 downgrade) towing my car and haven't had any issues. It's going up those hills that you need more patience... and of course your blinkers.
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