I was watching a Ford and a Chevy truck having a pull contest connected at their trailer hitches. The Fords tires started spinning and he was pulled backwards. To me it looked more like a traction issue than a power issue but thinking about it they would act the same to the casual observer.
What would the casual observer look for in this case to differentiate between power and traction?
Probably wheels that are NOT spinning like hell but biting or chunking and still being drug backwards.
The trucks have normal tires on them.
All i have to do is stomp the gas and start spinning out, and then you can casually drag me backwards all day, ive already blown my traction.
If it’s two trucks having a static tug-of-war, then it’s not a question of power-or-traction, it’s about torque-or-traction.
The truck that hasn’t lost traction won’t be operating at a high enough RPM to produce maximum horsepower; they probably won’t even be at a high enough RPM to produce peak torque, but in this situation, whatever torque they do produce (at the wheels) determines whether they win or not.
The truck that has lost traction has a couple of possibilities:
-if the tires are spinning on pavement, then they’re developing less traction than when they weren’t spinning. The driver has to let off of the gas to avoid bouncing off of the rev limiter, or let the transmission shift into a higher gear, either of which results in less torque at the wheels.
-if he’s in deep sand or very loose dirt and using paddle tires, then he’s flinging mass backwards, and his tires become reaction engines, similar to rockets or jets. If all the parameters are just right, then he could theoretically operate the engine at its max-torque condition, providing max torque at the wheels. If he makes more torque at the wheels than the other guy, then he wins. This is of course a bizarrely perfect hypothetical though.
Bottom line, these kinds of commercials only sway meatheads. If you really want an honest tug of war, put enough bricks in each truck bed so that nobody loses static traction, then see who wins. And again, even that doesn’t show which engine makes more peak power or torque; it only shows you which one makes more torque at a dead stop. That matters if you want to be competitive at a drag strip, but if that’s the priority, then pickup trucks shouldn’t be on the candidate list at all.
So, what exactly does a contest like that demonstrate? Obviously, Chevy wanted to make their truck look better than the Ford. I’m sure they meant to suggest that the Chevy was more powerful. But as long as both trucks have enough torque to spin their drive wheels, then the tug-of-war isn’t about torque at all. You could rig the contest (for lack of a better word) by putting bigger tires on one truck, or just letting some air out of the tires. Or if the tires were identical on both trucks, the winner would be whichever truck was heavier.
at static/very low speeds the engine will be limited by the stall speed of the torque converter, which will likely be set to the RPM where the engine is making near peak torque (or at least well into the meat of the torque curve.)
it’s just peacocking. Marketing does stuff like that too, like the dumb hoopla over a Toyota Tundra “towing the Space Shuttle.” Sure, it towed it for 1/4 mile at little more than a crawl.
For a mass-produced vehicle, yes, the stall speed will be high enough to ensure that the vehicle gets off of the line with some alacrity, but if you really want something close to peak torque at 0 MPH, then it takes an aftermarket torque converter (with a higher-than-OEM stall speed) to do the job.
Driver skill? Mechanically I suppose it could demonstrate a better-balanced weight distribution that delays loss of traction. And if the distribution is equal, the heavier vehicle wins.
The more widely applicable assertion would be that whichever vehicle has more weight over the drive axle(s) is going to win.
I believe that’s what I said, except with a lot more words. 
At some point, any piece of mass is going to be borne by an axle, no?
Yes, but whatever proportion of the weight is borne by a non-driving axle (if the vehicle has any) is going to be wasted.