The 80-series after around August 1992 introduced a viscous coupler over the centre differential. In order that this coupler doesn’t get stressed when in low range, Toyota deleted the manual centre diff lock switch and instead linked its operation to the transfer lever, locking the diff when in low range and opening it in neutral or high.
While this protects the transmission from erroneous usage, it does rather limit options, for example using low range when maneuvering trailers on hard surfaces etc. This needs to be rectified. continue reading…