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The fatigue properties of two series of truck forged components in as forgedand surface shot blasted condition were studied. The tests were performed in fullcomponents in a specially designed rig for such purpose. Both series of componentswere tested in constant and variable amplitude loading conditions. Constant amplitudefatigue loading was performed at amplitude 40, 45 and 50 kN on shot blasted and at 25,29 and 32 kN on as forged components. A specific spectrum was employed to test bothseries of specimens in variable loading condition, providing identical order of loadcycles in all tests. However the maximum load level was varied between different tests.The maximum load was set to be 50, 55 and 70 kN for shot blasted components and 45,50 and 55 kN for as forged components. The shot blasted components generally showeda longer life time in both constant and variable amplitude loading. A thoroughinvestigation on the fracture surfaces was done. The crack initiation and propagation aswell as the final fracture zones in both series were studied. A systematic differentbetween crack initiation points was detected. The fatigue part of the fracture surfacewas also investigated and the results were compared.