This paper describes the formulation of both “solid” and “thin-shell” isoparametric finite element models of an existing production light truck unitized cast iron gear carrier and its subsequent replacement. The emphasis of this study lies in the objective of deriving a method of using a thin-shell model for quick and cost effective design analysis purposes in lieu of complex and costly solid models. The analyses are studied in terms of redesigning the gear carrier to better optimize material usage, while simultaneously increasing the structural beaming fatigue life. The redesign is formulated by iterative thin-shell models with the final design verified by a solid model. A thin-shell model of the attaching stamped steel cover plate is also included as a separate study.