Tremec’s Magnum Six-Speed Will Separate Your Classic From Everyone Else. Tech | Transmission Upgrade One need not possess the mathematical skills of Einstein to grasp the obvious advantages of a six-speed gearbox over any old-school three- or four-speed box. With a deep overdrive in Sixth gear, those manly 3.91 or 4.11 axle ratios in your … Continue reading Tremec’s T56 Magnum Six Speed Manual Gearbox