 muddy or snowy), the car can move with traction in either the front or rear wheels.For the Celica, the original ST165 GT-Four of October 1986 had "Center Diff.Lock" with switch located near the hand brake, and starting from the facelift model of October 1987 came with transfer case contains a viscous coupling unit that provides 50/50 power distribution to the front and rear differentials at all times, as in the Previa All-Trac models.