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Harmonic problems

I have a 1998 f150 with a 4.2 . I putting the third harmonic balancer on it. The first went out at around 130,000 miles put the new one on and now 70,000 mile later it went out. They both sheared at the shaft. This is a basic to and from work truck no hot rodding. Any ideas?

Whoa. Harmonic balancer failures are pretty rare…they’re generally supposed to last the life of the engine. Are they factory or aftermarket balancers?

the first was factory the second was used from junk yard and the third 'aka the charm, i got on line. fingers crosed. i should mention i put a new long block in the truck and placed the first balancer on the new lonk block. other wise thats it.

Interesting article-

not your problem but interesting insight into potential failure mode. How did you install the balancer? Is your ignition timing at spec?

as far as i know it went great till it broke again. the last was instaled by a shop i have always been happy with and is at now.

Any oil leaks near the balancer?

Oil will rot the rubber part of the dampener, then it’ll shear as you suggest. Fix the leaks, then the dampener will stop failing.

thanks that makes sence