Most of us have replaced the both halves of the "rope" with the motor in the car. This was not an approved GM dealer procedure so the official manual does not promote the replacement of the upper half while the crankshaft is in place. In my case, I had success after I also replaced the main bearings and shimmed them as close to minimum clearance as possible. My previous two seals lasted about 100 miles. If you can adjust your mains at the same time, you will boost your chances of having good results.
