Mobile manipulators are comprised of robot manipulators mounted upon mobile platforms which allow for both high mobility and dexterous manipulation ability. Although much research has been performed in the area of motion control of mobile manipulators, previous developed models are typically simplified and assume only planar motion and/or holonomic constraints. In this work, the equations of motion of a three dimensional non-redundant wheeled-vehicle based mobile manipulator system are developed using a Newton-Euler formulation. This model incorporates a complex tire model which accounts for tire slip and is thus applicable to high speed and high load applications. The model is systematically exercised to examine the dynamic interaction effects between the mobile platform and the robot manipulator, to illustrate the effects of wheel slip on system performance, and to establish bounds on the efficacy of the simplified existing kinematic models.