The Mirage also debuted Mitsubishi's "Super Shift" transmission, a four-speed manual with a second lever for "low" and "high" range; effectively making the transmission an eight-speed unit. The "Super Shift" was not originally planned. However, Mitsubishi engineers had to make use of the existing "Orion" engine designed for rear-wheel drive applications making use of the longitudinal engine orientation. In the Mirage, sizing constraints as a result of the front-wheel drive layout required the engine to be mounted transversely, thus causing the carburetor to face forwards and run into icing issues. However, the primary implication of the Mirage's powertrain orientation — and the issue that demanded the unconventional transmission — was the mounting of the transmission beneath the engine. This required the gearbox to take power down from the clutch, an action not possible directly as this would have dictated that the gearbox rotate in the opposite direction to that required. To overcome this, the use of an extra "idle" transfer shaft was necessitated. It was subsequently realized that for a cost no more than developing a new five-speed transmission, this shaft could be modified as a separate two-speed gearbox controlled by a secondary shift lever mounted alongside the main lever inside the cabin. The ratios on this transfer transmission were, in effect, "underdrives"—consequently marked on the second shift lever as a "power" mode due to increased performance granted by the lower gearing. In contrast, the higher overdrive setting was noted as "economy". Mitsubishi called this a unique selling proposition.