I have the 2.5 Clayton with BFG KO 2s and my shop strongly recommended 5.13 gears. I think at 70mph 5.13s run at about 150 more rpms vs. 4.88. I did a lot of research on this and shops seemed to be about 50/50 so I went with what my shop recommended. I know one person who did 4.88s and wishes he would have done 5.13s. I know another person who has 4.88s and he is perfectly happy. Interestingly, I talked to a gear manufacturer who recommended 5.38s but no one else did. Basically I went with my shop‘s recommendation and I am happy. Plently of power and gas mileage is pretty much what I expected.I did the Clayton 3.5" overland plus, steering stabilizer, axle disconnect skid. Love it. I'm stuck between 4.88 and 5.13 gears. The 4.10's now drive pretty well but I need to make my mind up on gears soon. Lots of hwy, not much towing. I'm leaning 4.88 as it's pretty flat around here. Gas is creeping up and I did lose some power with 37's. Added a high flow banks intake to help some. Front drive shaft is on the list at some point as well. Those guys at Clayton were very nice and helpful. Top notch quality, made in USA to boot.