A vane pack assembly (25) for a variable geometry turbocharger (10) including a an upper vane ring (28) and a lower vane ring (30) and a plurality of single-axle, self-centering adjustable guide vanes (26) disposed in a turbine housing (20). The plurality of guide vanes (26) include a post (50) having a vane (52) formed integrally therewith. Each post (50) includes a convex self-centering pivot feature (56a, 56b) at one end adapted to seat in a complementary shaped concave self-centering pivot recess (48) of the lower vane ring. The vanes (52) are positioned between the upper and lower vane rings (28, 30) and pivot to control exhaust flow to a turbine wheel. The self-centering pivot features compensate for movement or deformation of the turbine housing (20) and vane rings (28, 30) due to the effects of differential thermal expansion.