We study the jamming transition in a model of elastic particles under shear at zero temperature. The key quantity is the relaxation time tau which is obtained by stopping the shearing and letting energy and pressure decay to zero. At many different densities and initial shear rates we do several such relaxations to determine the average tau. We establish that tau diverges with the same exponent as the viscosity and determine another exponent from the relation between tau and the coordination number. Though most of the simulations are done for the model with dissipation due to the motion of particles relative to an affinely shearing substrate, we also examine a model, where the dissipation is instead due to velocity differences of disks in contact, and confirm that the above-mentioned exponent is the same for these two models. We also consider finite size effects on both tau and the coordination number.