4.88 is what I think they recommend with 35's and manual trans in the 3.6 for optimum split on and off road performance. I have 4.56 in an auto and 35's. Its my daily driver and I drive about 20K miles a year in it so I wanted a little lower RPM on the highway. The installer did try to talk me into 4.88's, but coming from 3.21's, the gears I got feel like night and day. I'm happy with it.