The massive boom in the wireless technology has led to heavy utilization. Due to the heavy utilization and shared nature of resources causes QoS problems in ad hoc networks. Providing QoS is a severe problem in mobile ad hoc networks. The main focus of this paper is to analyze the performance of AODV and DSR routing protocols in MANETs under responsive and non-responsive traffic by varying the transmission rate. Apart from that, this paper also discusses the various issues related to congestion in ad hoc networks. Simulations are carried out using ns-2. The QoS parameters used in this paper are throughput, End-to-End delay and Packet Delivery Fraction. From the experimental results it is found that impact of transmission rate shows significant changes on the performance AODV and DSR. By increasing transmission rate throughput also increase but at a particular transmission rate, it is observed that there is a plunge in throughput; this point is call converging point to predict the congestion and asses the performance of the protocol. The authors found that performance of DSR is better in terms of throughput when compared to AODV under TCP traffic. There is no major impact of transmission rate on throughput for DSR under UDP traffic.