A drive mechanism module for use in a reciprocating pump converts rotational movement of a drive shaft to reciprocating movement of a reciprocating pump component transversely to the drive shaft. The drive mechanism module includes a connection member for attachment to the reciprocating pump component, a translating member that drives movement of the connection member in a first transverse direction while reciprocatingly translating in a second transverse direction relative to the connection member, a rotating member that rotates eccentrically with the drive shaft, and a rotary bearing assembly that permits rotation of the rotating member relative to the translating member while driving transverse movement of the translating member. The drive mechanism module may define a bearing fluid path for creating a hydrostatic or hydrodynamic fluid bearing at the interface of the connection member and the translating member.