Recent problem that happened for the first time this morning...... driving down hill near the bottom of road i heard a loud bang and jeep locked up and came to a standstill... i put it in 1st gear lifted clutch as you do and i didnt move.. then i put it in reverse and fine i reversed and everything was fine (i think) then i went down that hill again and the same thing happened. so i could do with some advise or info.... thank you!