A.J. , I have to deal with hills and small mountains on a daily basis and I too have the 3.7 . I am running 245/75s which I guess are like 31.5 " tall. My XK shifts out of overdrive at the very least incline but its just something you have to get use to. Eventually you will become use to it and ignore it. I've been running these for almost two years now with no issues what so ever when it comes to suspension or drive-train. Sometimes I wish my area was flat so I could get better mileage but then it wouldn't be as beautiful. This is what I have to deal with daily, its so sad.