A center bearing assembly rotatably supports an intermediate portion of a vehicle driveshaft assembly during use. The center bearing assembly includes a rigid bracket that is secured to a support surface of the vehicle, a support member that is supported within the rigid bracket, and an annular bearing that is supported within the support member for rotatably supporting the intermediate portion of the vehicle driveshaft assembly. The support member is formed from a resilient material and has a cavity formed therein. A sponge is disposed within the cavity formed in the support member. The sponge may be formed from any material that is capable of absorbing or otherwise retaining a quantity of a rheological fluid therein. A control circuit is provided for selectively generating and applying an energy field to the Theological fluid contained within the sponge and thereby varying the resistance to flow or shear thereof. As a result, the vibration dampening characteristics of the support member can be varied.