I ran the 6.1 trail tough gear set for over a year with stock gears and open diffs and it worked great for the most part, they will save your clutch and put most of the pressure on your u joints, the t.t. gears have better street manners, I think there only 16 percent reduction on the highway so 1.6 to 1 and 6.1 to 1 for the calc, just make sure you have the stock zuk u-joints (52.00 ea.) on the rear drive line.