Hi all, I have a new to me 2001 suburban, 4wd w/ a 6ish" lift and 35" tall tires. According to the PO the truck has 4.56 gears installed at the front and rear axles. It runs great around town but feels a bit sluggish going uphill. I was going up the pass out here and the truck would not go above 55mph. It felt like it was in overdrive the entire time. I shifted to from D to 3 and nothing changed. Any suggestions on where to start looking?