Every time I've had an auto trans with Sport and Regular drive modes, I stick it in sport, as regular won't go down a gear unless I press the gas so much it then roars into high-RpM neck-jerking acceleration.
Sport allows me to nudge the pedal and go down a gear, not like I'm trying to start a hill-climb race but like I just want to sit gently in the power band.
Point is, I suspect shorter gearing achieves about the same effect.
The ol' "You'll be cruising at normal highway speeds at 4000 RPM" argument doesn't really work today with our 6-speed (or more speeds) trannies.
Not exactly ...
Used to have a Caprice wagon with 2.56 axle.
I'll never fully express my ire after HOPELESSLY losing several races to what I THOUGHT was an essentially identical 2.93 wagon.
When he showed me the metal mech fan underhood, I actually exclaimed
"How the frak does that big @$$ metal fan make your fake@$$ woodpanel wagon quicker than mine?!?!" (Mine lacked fake wood paneling.)
No shift program in the world could ever possibly make a 2.56 wagon quicker than a 2.93 wagon (both 4L60Es).
Although I'm grateful to my wagon for goading me to learn LT1 pcm tuning (which protected the 4L60E far better than GM ever intended!),
3.42 was hands down THE best bang-for-the-buck POWER mod.
Going from 2.56 to 3.42 was far better than tuning, without question.
My 3.42 wagon left his 2.93 wagon in the dust like he'd done to my 2.56 wagon.
It was GLORIOUS - and I did not lose even 1MpG!
With 2.56, my wagon topped out at 131MpH (AFTER I lifted GM's 108MpH speed limiter).
It's actually more accurate to say I ran out of patience and began to fear for my engine.
The amount of time it took to go from 130MpH to 131MpH was roughly a long cigarette drag.
With 3.42, my wagon topped out at 141MpH, and took 3.42 far less time to get to 140MpH than it took 2.56 to get to 130MpH.
Better said, I ran out of bawlz, and don't care to personally find out how much the LT1 had left in it.
A credible argument can be made that, based on the top speeds, my wagon effectively gained 60 horses going from 2.56 to 3.42.
No way any tuning, even after upgrading from 87 to 91 octane, could ever possibly release 60 more horses from any 5.7L LT1 V8.
Those with 6L80Es, most likely have 3.08 or lesser axle gearing.
3.42 or 3.73 would REALLY liven those 6L80Es up, even without a tune.
3.73 would work even better for those with much larger tires.
Those SUVs with 4L60Es, most likely have 3.73 axle gearing, although some have even less.
Mine has 3.73. Every time I floor it, I die a little inside.
Having driven a Tahoe PPV that the owner blessed with 4.10, and witnessed no MpG penalty,
4.10 should be the minimum rear axle gear for ANYONE who wants / needs more power to the ground. 4.30 would work better for those with much larger tires.
Soon as I can afford BOTH 4.10 axles, it's getting both 4.10 axles.
If I'm wrong and it costs a highway MpG or three, it'll make up for it in smiles per gallon.