Had 4.88s installed then drove to Colorado. They did great on the highway and around town.

 

I am going 4.56 when I regear because of my duratracs, which are not a "true" 35.. If I go with a bigger 35" tire down the road, the gears will still be fine.

 

I'm going to put duratracs on mine 325/65/18 which is not a true 35. My next question is will the install kit for the 4.88 fit the 4.56, because I already have the Yukon 4.88 gears and install kits and if I go to a 4.56 so can I just buy the gears?

 

I don't think there's an easy answer. There will be things you like and don't like about whichever ratio you choose. I have 4.88 and 35's and I do a lot of highway driving a speeds 75 mph and up. My RPM's in 6th gear make it sound and feel like my engine is going to bust the hood off. The upside is that now I feel like I can go to 37's if I want to. I can also drive with confidence here in the mountains. But for most of the driving I do, it would be nice to have my engine working easier with the 4.56's.