How critical is axle ratio?

Hemling wrote:
In the modern day of 10 speed automatics, how necessary are 'towing' gears? By 'towing' I mean anything over 4.xx. These new transmissions have such low first gears compared to just a decade ago, is it really necessary to get deep gears anymore? I understand it makes getting going easier on all the moving parts, if you have a 4.30 compared to say a 3.55 or something, but doesn't it all come out in the wash? What I mean is, a truck with lower numeric gears will just tow in a lower gear, while a truck with deeper gears will allow the transmission to hold a higher gear. Is there a tradeoff or 'sweet spot' that anyone can speak to? I am still towing with an Excursion, so everything is a trade off. I could install 4.56 gears, but only have 4 gears. I could keep 3.73 gears, but know I'll always be in 3rd or 2nd to pull. I know that the towing guides always list bigger weights the deeper the gears get, but with a modern 10 speed automatic, I'm just not seeing the big deal anymore.

The big deal is in getting the load moving. The 3.56 will start a load from 0 much better than a 3.15 will start a load from 0.. Yeah once you get moving you may be able to find a gear it will be happy in. But moving it to begin with will be much harder, as the 3.73 provides much more torque, and torque is what moves the load.

Go out and put the selector in 2nd, or 3rd gear, and try to move the load. Is it harder than first? That is the difference. The ratio not only changes the gears while running down the road. It also changes the starting gear power.