Does anyone know if the Trailer Provision option has a lower (less mpg) rear gear(oops, sorry, fwd, gear) ratio?
Also, if so, what is the "normal" (no Trailer Provision) rear gear ratio?
I am quite sure the gear ratios are the same. You get a "tow/haul" button with the towing package that changes the transmission programming. This (and the larger cooling system) allows 4500 pounds max towing vs. 2000 pounds with an aftermarket hitch and no towing package. If you plan to tow at all, I would strongly recommend getting the package because there are also issues with the fuse box in non tow package vehicles that prevent using the trailer light wires. (Some people have had it fixed under warranty and others have paid to get it upgraded.)
3.16 means the tires turn 3.16 times slower than the output of the transmission.
The other gears listed above mean the transmission turns X times slower than the engine (Actually equal for 5th gear and faster for 6th (overdrive)).
I just went out at lunch time and checked some of the numbers. Assuming about a 29 inch tire diameter (estimated), I calculated the speeds at 45 MPH to be-
3035 RPM in 3rd
2325 RPM in 4th
1650 RPM in 5th
3000 RPM in 3rd
2250 RPM in 4th
1600 RPM in 5th
So the table above looks like it's correct. (Assuming some small errors in tire diameter, tachometer accuracy & speedometer accuracy).
Higher final drive ratios generally mean more "pull" (more torque at lower speed for the same horsepower), lower top end speeds, and somewhat lower mpg (more friction losses due to higher engine speeds).