In July i went up the Green River Gorge on I-26 in North Carolina it's a 7% Grade. Coming from South Carolina. I was doing 3000 RPM at 40 MPH in the right side truck lane. My truck is a 2002 Dodge Ram...
Others will call that "struggling" LOL... just puts good used trucks on the market for those in the know :D
My 97 F150 with a 5.4 and 7000 ish lbs loaded and similar power specs with 3.55 would hold about the same speed in second gear. That was fine because I was in peak tq range. The truck pulled right along. No problems.