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Year, engine, and miles?
Just a WAG - seems like just the link plates only on the front side are failing?? - perhaps the pulleys aren't lined up, or perhaps bent, causing the chain to be flexed sideways a bit?
I've never seen anything like this. Be sure to let us know how things turn out.
1989 F150 XLT standard-cab shortbed 4x4, 5.0L, AOD, 3.55 gears, manual hubs, 31x10.50 tires, 218K miles. Repainted Oct09. SOLD - Jan2015
2014 F150 XLT standard-cab shortbed 4x4, 5.0L, 6-speed auto, 3.55 gears, auto hubs, locking diff, trailer pkg, 3K miles.