Transmision trouble..... :grrrrrr: l was driving normally today and when my truck shifted into 3rd it went booom and rocked the whole truck. When its in D or in 3rd gear its like its in neutral. it will drive in 1st and 2nd gear and reverse only... its only got 71 000 miles on it and they say i need a new transmission:grrrrrr:. l believe them but i can not understand why this has happened so early. its got the 4.3 liter engine with the 4 speed. anyone else have this happen?