i know this is late but i just seen this. the old t-case works as an open differential. when the front tires spin the brakes have to be applied to transfer torque to the rear wheels. and at the track this is a mess, and causes horrible 60' times. plus the stock case is weak and it was showing its colors. the 149 is stronger and all the torque transfer work is done via the viscus coupler in the case its self. which means no more brakes applied on the launch.