Vehicle durability mission loads are an essential and decisive for a reliable life prediction for the component through any durability evaluation. One option to calculate mission loads are multibody models to represent vehicle’s suspension degrees of freedom (dofs) and its dynamic behavior. Generally, trucks have greater wheelbase and then lower natural frequencies than passengers’ vehicles. Therefore are more suitable to dynamic body excitation and the ordinary consideration of a rigid body shell is not relevant.The proposal of this work is to compare the chassis loads considering rigid and flexible frame mounted over the primary suspension. A pseudo-damage was calculated with chassis loads time history for severity assessment. The chose vehicle for the study is an Iveco 4×2 medium range, 6850mm of wheel base, with gross weight of 17ton and leaf springs primary suspension on both: front and rear axles.