gravity. The other new arrival was the Prisma 4WD, featuring a two-litre fuel injected engine and Lancia's three differential permanent four wheel drive. Derived from the flagship Thema, the 1995 cc, twin-cam 8-valve engine featured two counter rotating balance shafts and IAW fuel injection; it developed and . The 4WD package was completed by four disk brakes from the 1.6, power steering and wide, low profile 185/60 tyres on 14-inch 8-spoke alloy wheels. Minor details set the 4WD apart from other Prismas: outside a "4WD" script on the right half of the grille and on the new side skirts, inside it sported the instrument panel from the Delta HF 4WD with six round gauges, yellow scales and hands. In June 1987 the 4WD was updated and rechristened Prisma integrale; it came with standard two-tone paintwork in a choice of three tone on tone combinations, a matching Alcantara interior, and a drop in price from the 4WD — at least in the home market where prices were cut by 10 percent. The last update for the Prisma was the introduction of the eighth model in the range, the upmarket Prisma 1.5 LX, in March 1988. The LX trim added metallic paint, checked cloth interior with beige carpeting and convenience equipment. The successor of the Prisma, the Lancia Dedra, was unveiled in early 1989, with sales commencing in May; production of the Prisma ended in 1989. Four-wheel-drive system Lancia's permanent four-wheel-drive system was based on three differentials. An epicyclic gear train served as centre differential, splitting the torque between the front and rear axle according to a fixed predetermined ratio—56% front/44% rear on the Prisma 4WD. The ring gear of the epicyclic differential meshed with the gearbox output shaft, its sun gear transmitted torque the front open differential, and its planet carrier, through a pair of bevel gears and a three-piece drive shaft, to the rear differential. A Ferguson coupling controlled the centre differential, preventing excessive relative slippage of the two axles. The epicyclic differential, the Ferguson coupling and the front differential were mounted coaxially in a single transverse unit just behind the engine. In place of the complex Torsen rear differential of the Delta HF 4WD, the Prisma 4WD had a simpler "open" type one, with differential lock—useful at low speeds in low grip conditions—controlled by the driver via a switch on the dashboard. This difference reflected the different goals of