My guess is they realized how close together 3.55 and 3.92 actually are in real-world use. Switching to 3.21 and 3.92 actually gives buyers better choices based on how they want to use their truck. Going to 3.21 probably gave them better mpg numbers as well.A question I doubt anyone here can answer. Why did they drop the 3.55 rear end.
I would argue that it's not the most preferable. I had my truck built, optioned it out very well, and knew I would be using it to tow heavy and frequently. 3.55 work very well for me at the truck's max tow rating or slightly above.There's a reason the 3.92 is an at-cost option. It's the most preferable ratio.