Just the top perch adjustment. have beaten the crap out of it and wheeled it pretty hard. There is a little rubbing in the rear, nothing serious. The key for 37's to clear is to use the stock wheels. 37" all terrains are even a little smaller and narrower than the projects so they clear pretty well. I put them on before i even had 500 miles on the truck so i didnt notice the power loss. If your truck is your d/d I dont recommend the projects. it takes about 3 to 5 miles to round out the flat spots.
