Galvinized is probably right. Now hope that the shafts are OK. When installing new one use a grade 8 1_4 bolt with unthreaded shank which exstends the full width of the coupler and then double nut or lock nut it. Sometimes the bolt will break and allow the coupler to slide and wear on only a small area. Also drill it 90 degrees off to accept a 1_4-28 thread zerk and grease it once a year wheather it needs it or not. The coupler is not hard as it is desirable for the coupler, not the shafts, to wear out and be easily replaced. It is not hard to pull hydro w_ a come-along to hang it from and some plug corks or caps. Maybe it was time to change hyd oil anywayIJ lol