In this study, the effect of stiffener plate thickness on stress of truck chassis using finite elementrnmethod focusing on Volvo truck chassis is performed. The main goal of the research isrnoptimization of stress on joints of the chassis by adding stiffener plates between joints of sidernmember, cross member and on top of connector plate flanges. The stiffeners are fastened byrnmeans of bolt and rivet. In order to achieve reduction in magnitude of stress on joints of thernchassis stiffener plate thickness are varied (3mm to 8mm). For analysis, High strength low alloyrnsteel existing truck chassis structural steel material is used. rnrn rnAnalytical analysis of maximum stress and maximum deformation are done on existing chassis tornselect the cross member for further modeling and analysis. Both existing and modified truckrnchassis drawings are modeled using CATIAV5R19 and the finite element analysis is done usingrnANSYS14.5. rn rnThen, the finite element analysis result showed that the magnitude of equivalent (von-miss) stressrnusing stiffener plates thickness of (3mm-8mm), the value of the stress reduced (190Mpa77.6Map)rnrnrespectively and according the result (36.9% - 59.0%) of stress optimized. Thernmagnitude of deformation using stiffener plates thickness of (3mm-8mm), the value ofrndeformation reduced (0.34mm-0.266mm) respectively and according the result (11.8% - 22%) ofrndeformation optimized as compared with existing chassis. Due to stiffener plate thickness ofrn(3mm-8mm) added to existing chassis weight of modified chassis is increased (72.69kg - 89.52kg)rnrespectively and according the result (9%-18%) of weight is increased. Finally, the finite elementrnanalysis results comparable with literature results and the difference is less than 10%.