Why are my lower ball joints destroying my cotter pins?

[PushnFords]

Hmmm.... I'll try that again, but last time I cranked it down the nut was basically clearing the cotter pin

I've found that a lot of replacement ball joints and tie rod ends have shorter castle nuts that go past the cotter pin hole. I keep a box of assorted castle nuts around...along with larger cotter pins...biggest ones that will go through the hole. You might need to get some different castle nuts.