2013 Silverado LTZ Z71

The OEM gears are 3.08 and with 33” tires it’s already a dog. 5.3l 6sp tranny.

I still do a lot of long distance highway driving and occasionally tow the Baja272 or a loaded cargo trailer. Trips are usually less than an hour but may step up to a few four or five hour drives with some grades.

4.56 seems a tad overkill but checking with the OSO brain trust for real experience.

The 6l80 is one of the newer transmissions that DOESNT have a 1-1 gear somewhere BUT forth gear is close at 1.15. Currently in 6th gear (.67-1) it turns your 3.08 into 2.06 -1 final drive. A 4.56 x .67 would be 3.05-1, if you were to put your truck in 4th gear and drive it, the rpms would be fairly close to what a 4.56 would feel like just to see IF at highway "speed" you were ok with it, personally a 4.10 is probably better overall. Check your driveshaft length too and go on spicers 'critical speed chart" and see where THAT magic number is before going with 4.56s, IF you drive at 90 on highway empty like some of us, you may find you may possibly have a terrible vibration, the chart doesnt lie, just chased this on my duramax with stock tires and stock gears with smaller but HD steel driveshaft, Smitty

THANK YOU! Invaluable input as always, Smitty.