A proper crack repair starts with diagnosis. Ground movement, curing shrinkage, tree roots and slabs carrying loads beyond their design all produce cracking, and they need different responses. Fixing the crack without addressing what caused it simply means seeing it again, usually in the same spot. From there the method follows the crack: flexible sealants for hairline surface cracks, routing and filling for wider stable ones, epoxy or polyurethane injection where a structural crack has to be stabilised and bonded.
Toowoomba weather makes prompt repair worthwhile. A summer storm cell puts a lot of water into an open crack in a very short time, and on the reactive black soil through Wilsonton, Glenvale and Harristown that water is exactly what starts the slab moving. Winter adds a second mechanism, as moisture sitting in an open crack through a hard frost works the edges apart a little further each season. A properly repaired crack should stop moisture ingress, remove any trip hazard and hold up over the long term.
A site assessment confirms the right repair approach for your driveway and whether anything else needs sorting first.