GMC recently released a new ad featuring its "Pro Grade Protection Plan" for the 2013 Sierra, in which the truck had heavy-duty chain pulleys attached at each corner. The ad claims there were no "stunt doubles" and that the truck was lifted 46 times with the pulleys.
While impressive at first glance, when you take a closer look at the physics involved in the ad, it makes one wonder how truly grueling the demonstration really was. The truck in question was a Sierra Denali. The truck weighs 5377 lb, and has a front/rear weight distribution of 58/42 in AWD form. That would put the approximate weight per attachment point at 1559.33 lb in the front, and 1129.17 lb per corner in the rear. That does not take into account the lateral stretching forces at play, but some online sleuthing revealed that a 45-degree angle on a strap (or presumably chain) decreases its pulling strength by half.
Typical aftermarket replacement tow hooks listed a capacity of 10,000 lb. Even taking into account the assumption that a 45-degree angle on the hook (not the strap or chain) puts double the load on it, that's still about the equivalent force of 3000 lb per hook in front, and 2300 lb per hook in rear. So although the ad may appear to be an impressive feat of strength, it also appears the stunt was well within the Sierra's design and engineering parameters.
Again, I am looking at this as a non-engineer, and am applying a rudimentary layman's perspective to the physics at play. If you're an engineer, and have a different take on the Sierra ad, and how it does demonstrate the truck's exceptional strength, please share your insights below.