Everything was going fine today until I was rolling to a red light in neutral at about 40 mph and the light turned green. I popped it into 4th gear and wham this extremely loud grinding sound. I pull my jeep over and then I try to put it into 1st to move and there is the grinding again. Had to get it towed, because she wasn't going anywhere. Also there was a humming noise that I have been ignoring for awhile that I thought may have been the transmission, now this has happened. Hoping I wont need a full transmission swap, what do you guys think?