I don't think that's bad since I can tow 10,000 pounds if I want to.
The 3.21 can tow just as much as the 3.92. It just means that if both trucks are stopped and then floor it, the 3.21 will take a little longer to hit 20 mph but beyond that both trucks have the same gears available. Both trucks will feel just as strong pulling up a mountain, or passing a semi on the freeway.
Tow capacity numbers are really
marketing numbers. My truck is "rated" to tow about 8500 or thereabouts, but nothing wrong happens if I tow 10,000 instead.
The real number that matters, is payload. That's an
engineered number based on rear axle ratings and suspension, and both trucks are identical here. The simple truth is, based on travel trailer tongue weights of 10 to 15 percent, neither your truck or mine can actually pull more than 8500 without exceeding payload.
So no, in most cases you can't really pull 10,000 pounds without exceeding the most import limitation of your truck: payload.