Some of the best money I have spent was going from 3.90 gears to 3.38 gears. My 56 runs quieter with better mileage. It cruises just fine at 70 mph with 29-inch tires along with a very healthy 235. I have no noticeable loss in acceleration. It still tows my boat and it drives up to Tahoe just fine. My experience with gearing up is very positive. It was worth the money. 4.11 to 3.55 should be similar, if the rest of your truck is up to the extra speed.