I have a 1995 RHD jeep Cherokee sport 4.0 and was driving down the road when it felt like the left front locked up, rear end swung around and almost rolled because I was going 50mph. Making a terrible roaring noise, or vibration as mechanic says, rear end had very little grease in it however there was no broken metal or gears seen when removing differential cover. Replaced gasket and filled with new oil, but the noise is awful and don't understand what cause it to lock up and jerk to the right! Any ideas? TIA!!