Ihave been running a Rock-On 4L60E for quite a while now. The car has dynoed 638 rwhp. It's a full weight car with no weight reductions. Air conditioner still blows cold air. Last time out it was running 6.7s in the eighth at 105 cutting low 1.5 60' times. My son has a 99 Z which also has a Rock-On 4L60E in it. He has a few more horsepower and a little less weight than I have in mine. His is running 6.4's and cutting 1.3 60' times on a small shot of nitrous. Next time out it will be jetted a lot bigger. We are hoping for 6.3s which would translate to a 9 second quarter mile car. It is also a full weight car with working air conditioning. Our Rock-On trannys have worked great. They are handling anything we throw at them. I wouldn't hesitate to recommend Rock-On trannys. In case anyone is wondering, we paid full retail for aour transmissions.