Have '98 XLT, 5.0 L, AWD, 4R70W tranny. 228K miles. Except for brakes, shocks, tires & tuneups have only had to replace front end (ball joints, TRE's, upper & lower control arms) until this week. Driving along at 45 mph starting up a hill and heard a loud "thunk" and stopped moving. No prior...