The first variant of the Lamborghini Diablo, the VT was introduced in 1993. The VT was offered as a coupe, or as the VT Roadster. The greatest difference between the VT and the Base Diablo was the introduction of a variable four wheel drive system. This new system used a viscous traction center differential, thus the name VT. This differential allowed for 25% of power to be sent to the front wheels when necessary in order to limit wheel spin and improve handling. The VT was produced in two generations, with the large majority of the cars sold being first generation. From 1999 onwards, the VT featured new fixed headlights, as well as various mechanical and interior upgrades. Manufacturing shifted to the new and updated VT 6.0 in January 2000, until the end of Diablo production in 2001.