For the 4x4 navara and brte the rear suspension design is leaf spring over axle while the 4x2 has the suspension design of axle over leaf spring. Advantage of leaf spring over axle is the grest suspension travel translating to the better rieing comfort, set back is the carrying capacity.... Max payload of the 4x4 is only up to 800 kgs. The 4x2 was designed as a workhorse with a max capacity of 1 ton.