The 3.08 axle ratio likely means your truck is rated to tow up to 6700 lb. Towing more than that isn't going to make it blow up. It will have to shift down more on the steep grades than one with a higher ratio axle. Your engine makes peak HP around 5200 rpm and peak torque around 4000 rpm. When it is needing power to pull grades it will need to run in that range of rpm. For towing tag trailers (non fifth wheel) a stabilizer hitch makes towing a little safer.
Although I can't recommend doing it, I've towed trailers that weighed double what my truck was rated for.....I've never had a problem.