Things get ugly on 'American Chopper: Senior vs. Junior' (Thu, 9PM ET on TLC) when the bitter feud between Senior and Junior comes to a head on a radio show.

The father and son have not talked for the better part of a year, and, when the discussion turns to a lawsuit Senior has filed against Junior for his share in Orange County Choppers, curses fly, and the two begin speaking over each other in a heated exchange.

Tensions escalated between the two last season when Junior was fired from Orange County Choppers and started a custom bike business in direct competition with his dad.