Recently some Sport Trac members have reported experiencing harmonic balancer failures that have resulted in repairs ranging from minor to moderate repair costs. In one case the repair was limited to replacement of the failed balancer and reinstallation of the serpentine belt. In another case the balancer, crankshaft position sensor and serpentine belt had to be replaced in addition to a towing bill due to being stranded on the highway. The harmonic balancer failure has not been limited to Sport Tracs. It has also occurred on 1st generation Explorers. I have not read anything in Ford's documentation about the expected life of the harmonic balancer nor the warning signs of its impending failure. I suspect that the serpentine belt slipping off track may be an indicator. I think it would be helpful to members if those who have experienced a harmonic balancer failure would share their experience with emphasis on the age and mileage of the engine and any warning symptoms realized in retrospect. Did you notice that the belt tensioner was moving in and out due to the balancer rotating off center? Was there a sound coming from the area of the balancer due to it rubbing against the crankshaft position sensor? Please post any photos you may have of a failed or damaged balancer. Thank you in advance for sharing!