All-Trac

All-Trac was a proprietary full-time four-wheel drive system used on a variety of Toyota badged models and the nameplate was used from 1988 to 2000.

It was considered a revolutionary advance for four wheel drive automobiles into the mainstream consumer market and its electronic/vacuum controlled locking center differential was rare in a passenger car.

For all manual transmission models except Previa, and the 1988 and newer Celica, there is a small button inside the vehicle labelled 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.

The vehicle should not be driven with the viscous coupling disabled as transfer case or transmission damage will occur.