Your transmission is going to hate you.
If the truck has the tow package it has the trans cooler—which is a great thing.
Plan on 35mph with your foot down and in 2nd or 3rd gear on the steeper part of the passes.
Good trailer brakes and controller are a necessity. Don’t let the occasional towing flat lander tell you any different. Pull the wheels off the trailer and check the brakes. Keep it in the lower gears on the downhill side.
10k ft altitude means ~10-15% less hp compared to sea level for a normally aspirated engine. Thinner air means lower density and reduces cooling effect significantly. Vehicles that operate just fine in 110 degree Texas weather overheat at 80 degrees at 8k ft in altitude while climbing the pass. Often.
Agree about the brakes. Mine were FUBAR from salt on my trailer when I bought the boat, and I used it that way for a while, then completely rebuilt the hubs/brakes with stainless Kodiak parts, so I’ve experienced it both ways. Brakes= better.
My first-Gen with the 4.7 has no issue holding 60 mph, granted at lower altitudes, with steep sections of the Coast Range; did it just the other day because we finally got a calm patch in the ocean and it was time to slay some lings.
If the OP is talking about a first Gen truck, which I had ass-u-med because most of the later ones have the 5.7L around here at least, brakes are the main weak point for towing. And yes, use the “OD off” button. In overdrive the tranny will be using the torque converter up the wazoo which equals heat. Heat bad. The 4.7L loves to rev anyway. Just drinks gas when it does.
Tundras are beloved in the PNW. A lot of guys tow way heavier than 3k with them routinely. Especially the later models. The 4.7 and 5.7 drivetrains are proven excellent.
Now how the new hot-rod small displacement V6 holds up is still TBD.
