2004 Lexus LS 430 w 150000 miles. 6 speed won't shift from 3 Rd to 4th gear. Brought to Lexus dealership. Was told there was metal in pan and needed a new transmission. I know that all pans have some metal in them. When I told this to dealer rep he said that maybe they could do a valve body (?) Job. What is that? Do I not need a transmission?