Friction stir welding (FSW) has attracted many attentions in both academic and industrial sectors due to its promising characteristics compared with other conventional joining techniques. However, it still needs some improvements to become reliable and cost-effective for industrial applications. In this study, the aim is to develop a right angle friction stir welding (RAFSW) technique to assemble large side panels of truck boxes so that the technique be industrially reliable and cost-effective. For this purpose, Taguchi method and artificial neural network (ANN) modeling were used to design the experiments and optimize the welding process parameters. The efficient working window of welding process parameters was obtained at traverse speeds as high as 1700 mm/min. Then, the technique was developed to operate in force control mode using a spring load tool holder and a newly designed tool with a tapered entry. It is shown that the developed technique could tolerate high levels of joint fit-up disturbances like big gaps between the sheets before welding. Moreover, it was demonstrated that the developed technique could be operated using large, low-cost, CNC machining routers and with clamping only at the corners of panels. The use of weld tags prior to welding was beneficial in order to reduce clamping and distortion while maintaining a high strength level along the joints. NX-NASTRAN Finite Element software and various experiments including static and fatigue tests of the panels were used to design and evaluate the welded assembly. It was found that the developed RAFSW technique has the potential to be used for truck panel assembly.