NOTE guys! Did you use sealer on the keyway before you put the balancer on? They call for this in the book! My balancer never failed, but my crank pulley bolts broke and there was this weird knocking noise. It sounded like a bottom end knock. My mechanic told me to pull all the belts off and run the motor momentarily to see if the knock goes away. I never made it that far. When I was pulling the belts off i noticed the crank pulley was a little loose. Then I reached in to check the bolts and the bolt heads (all 4) came of with my fingers. I removed the balancer, drilled into the bolts and used a snap-on extractor set to get them out. That was tricky......hard steel bolts in an aluminum damper. Nevertheless, I got them out. I then went to a bearing supply store and used grade 8 machine allen head cap screws, lock washers and a little bit of red-loctite to re-attach the pulley to the damper. When I was re-installing the damper, thats when I read up in the book that you have to use a little sealer on the keyway before you put the big bolt back in.
When my crank pulley let loose, it did dink up the balancer a bit.....it was slightly bent. Later on I replaced it all with a good used one.
That was 5 years ago and no trouble since. I check all 5 bolts every oil change to make sure they are still there! Good maintenance tip since these cars were balancer breakers!