The instability of the thermal characteristics of rotating-blade coupling (RBC), with longitudinal ribbed turbulators, in real-time four-wheel-drive (4WD) vehicles has been investigated. The key parameters approximate to, the operating conditions of a real vehicle. The co-axial rotating channel flow exhibits a pattern of unstable Taylor vortices. Longitudinal ribroughened walls were employed to prevent high temperatures in local regions. The local temperature-distributions of the RBC with longitudinal ribbed turbulators were measured and compared with those with smooth walls. Longitudinal ribbed turbulators can: (i) prevent local increases in temperature, (ii) increase the lives of the parts of a rotational blade connector and (iii) protect the motive sources of 4WD vehicles. (C) 2004 Elsevier Ltd. All rights reserved.