Well gang,
I have the exact same model/year/engine/trans as the OP. Yep, as has been stated, if the 2nd gen of the Rubicon was starting out on the assembly line as an stick, then the Jeep was to be fitted with 4:10 gears. But, if it started life as an automatic, it was to be fitted with 3:73 gears. But, if you (the dealer or, a private person that ordered the Jeep) wanted both an automatic AND 4:10 gears, the line was happy to change from 3:73 to 4:10 gears, for a measly $600 back then. I have no idea what it costs now for a line change.
Ok, enough history on Jeep building. Yes, our '15 Jeep JKUR was outfitted with the automatic AND a set of 3:73s. I'd know the performance of that engine, its acceleration, hill and grade climbing capabilities and more with all the bone stock wheels and tires. I knew EXACTLY how it performed in all given driving scenarios.
In outfitting our new Jeep with a leveling kit and some Mopar HI-top fender flares, I knew it was time for some 315 tires which, as most of you know, are the same exact tire as a 35". So, on they went. A set of Hancook Dynapro 315 x 70 ATs on 17" x 8" American Racing Anson Off Road Alloy wheels.
Well, knowing the performance of that jeep as well as I did, I knew right off the bat, that EVERY driving scenario was hindered. Now, I lived with this set of operational conditions for about a year. Finally, I decided to re-gear. I knew that going to 4:10s would be marginally better so, I opted for 4:56s.
From the very first take-off, I realized I'd not only got BACK all of what I lost in acceleration but, gained a tad more than stock. Now, a "tad" is subjective. The thing you have to realize is, in a situation like mine, EVERY single time you accelerate from a stop sign, stop light etc. you use a certain amount of throttle. If you know and retain just how much throttle is used from a stop sign, going up hill, with stock gearing and tires, then throw a set of larger tires on making any compensation, YES, you KNOW what you lost in acceleration WITHOUT using MORE throttle.
And, just like take-offs, climbing grades and using specific gears, was also labored with larger tires and stock gearing. But, with the change to the 4:56s, I'd gained back my hill/grade holding capabilities with NO ENGINE MODS what so ever. Every single take-off, every hill, every grade etc. is now easier or, I should say, less throttle is used to cover the same ground, at the same speed.
This is one of those things that you have to know your vehicle and how well it performs, BEFORE any changes to really gain insight as how it performs AFTER the tire size change.
Scott