The differential carrier on 1988-89 models is a conventional type. If one of the rear wheels loses traction, the other may remain stationary. Beginning in 1990, the Celica was equipped with either the conventional or torque sensing limited slip differential.
One sure-fire way to differentiate between the two is to jack up the rear wheels with the transaxle in a gear. If the vehicle has the conventional type carrier, as one of the rear wheels is spun, the other will rotate the other way (in reverse). If the vehicle has the torque sensing type, neither of the rear wheels will be easy and may be impossible to rotate.