Im hoping someone can give me some advice on re-gearing. I have an 08 Silverado 4x4 ext. cab with 5.3L V8. I have 7 1/2 inches of suspension lift and Im running 35 inch Toyo MT's on 20 inch rims. I have a catback flowmaster 1 in 2 out and a K&N CAI. I drove it on the highway for about a 6 hr. round trip and the transmission kept having to downshift when going up an incline. I have been considering re-gearing and have read on here to go with 4.56 gears. Does anyone know what this will do to my gas mileage and what kind of rpm's the truck will be running at highway speeds (70 to 80 mph)? Would I be better to go with 4.11's? My real concern is I do drive on the highway on small trips every now and then and do not want my engine having to run at 4000 rpms because the gears. Thanks for any help!