mobile ad hoc networks (MANETs), the provision of quality of service (QoS) guarantees is much more challenging mainly due to node mobility and resource constraints. Therefore it is important that routing protocols incorporate QoS metrics in route finding and maintenance to support end-to-end QoS. The traditional AODV protocol seems less satisfactory in terms of routing data to end systems. Many revisions are done to the traditional AODV protocol to meet QoS challenges focused on bandwidth, end to end delay, Packet delivery ratio, energy and mechanism overheads. Hence , it becomes very necessary for MANETS to have an efficient routing and QoS mechanism to support various application. This article extensively and exclusively studies the issues involved with QoS routing and presents an overview and comparison of existing QoS based revisions done on AODV protocol, thus providing the reader with insight into their differences and allows to highlight trends in protocol design and identify areas for future research. Keywordsof Service, QoS metrics, MANET, AODV, Routing.