The Toyota pickup (upon which the 4Runner was originally based) underwent a major redesign in 1983 for the 1984 model year. Many other automakers were introducing mid-size SUVs in the mid 1980s (e.g., Ford Bronco II, Chevrolet S-10 Blazer) and the pressure mounted on Toyota to develop a competing model. Instead of developing an entirely new vehicle, Toyota took their existing short-bed pickup frame, made some simple modifications, and added an open one-piece body with a removable fiberglass top (much like the full-size Ford Bronco and Chevrolet K5 Blazer).
Thus, the first generation 4Runner is nearly mechanically identical to the Toyota pickup. All first generation 4Runners had two doors and were indistinguishable from the pickups from the dashboard forward. Nearly all changes were to the latter half of the body; in fact, because the rear springs were not upgraded to cope with the additional weight of the rear seats and fiberglass top, these early models tend to suffer from sagging rear suspensions.
The first 4Runners were introduced in 1984 as 1984 1/2 models. For this first year, all models were equipped with black or white fiberglass tops. An SR5 trim package was offered that upgraded the interior: additional gauges, better fabrics, and a rear seat were standard with the package. All 1984 models were equipped with the carbureted 2.4L 22R engine and were all available with a four wheel drive system that drove the front wheels through a solid front axle (although this would be changed in 1986, much to the chagrin of many off-road enthusiasts).
1985 saw the arrival of the electronically fuel-injected 2.4L 22R-E I4 engine (though the carbureted engine remained available until 1988). Additionally, rear seats were available in all 1985 4Runner trim levels, not just the more upscale SR5.
In 1986, all American-market Toyota pickup trucks (and the 4Runner) underwent a major design change as the suspension was changed from a solid front axle to an independent front suspension. Track width was also increased by three inches. These changes made the trucks more comfortable on-road, and improved stability and handling. However, this change arguably decreased the truck's off-road capabilities. Outside the US, the Hilux Surf (similar to the 4Runner) also gained the new independent suspension design, marketed as Hi-Trac. The pickups in those markets retained the more rugged and capable, if less refined, solid axle configuration. The 4Runner grille changed from the three segment type to the two segment grille on all 4Runners in 1986. Tops were color-matched on blue, red and some gold 4Runners, while other body colors were still sold with white or black tops. During 1984-1986 many 4Runners were imported to the US without rear seats. With only two seats the vehicle could be classified as a truck (rather than a sport vehicle) and could skirt the higher customs duties placed upon sport and pleasure vehicles. Most had aftermarket seats and seat belts added by North American dealers after they were imported.