no upgrade just cut out the diff casing in order to let rocks and dirt pass thru without it getting stuff in the diff chewing up belts.. you have to take the car apart to do it it takes about 20 mins to do each one...i onli modded the rear and have seen no signs of wear on the front belt so i didnt bother to do it..ive had the car about 8 months now and have onli need to change one rear belt b4 i did the mod. since i modded the rear i havent had another problem since.