rrcjr1972 most likely you are fine its just the truck shifting into second. you can hear it shift cause your shift point is way to early you need to tighten it up so it shifts later and then you will be able to hear it. as far as locking your diff you can give us a call and we can walk you through it or you cna go to our website http://www.cenracing.com/download.html once there scroll to the bottom you will see addtional information section and genesis diff lock is in there .