When going to a dual overdrive manual transmission like the TREMEC Magnum 6-speed with 2.97 first gear and .50 overdrive, it opens the door for more rear axle gearing to increase street performance, and still have highway cruising capability. But not enough rear gear and you end up cruising at too low of an rpm which can cause the engine to lug. In this snapshot, we have a typical combo of 3.23 gear, 28-inch tall tire, and a cruising rpm of 2,200. In fifth gear at 2,200 rpm you’re already going 76 mph. Changing the rear gear ratio to 3.73:1 or 4.10:1 would be much better.