Within the scope of this work, the effect of the position of the stiffening ribs used in the arm transition regions of a heavy-duty truck rear axle housing prototype on fatigue failure tendency was examined. In the vertical fatigue tests applied to the housing prototype, it was observed that the component withstood the targeted number of load cycles, however suffered fatigue damage at the lower stiffening rib - spring support connection area above this limit. To determine the effects of rib position on stress distribution of the part, firstly the vertical loading test was simulated using Finite Element Analysis (FEA). It was determined that the stress concentration region and the area where fracture occurred in the tests overlapped. Design improvement including relocating the stiffening ribs was applied to the housing model to decrease stress concentration at the critical regions. Results indicated that it is possible to reduce the maximum stress at the crack initiation region by approximately 41%. It was also concluded that placing stiffening ribs at the upper region of the axle housing could enable a lighter design.