rear front diff mount gone...theres 3 diff mounts on there rear diff left ,rear diff right ,and rear diff front ...its usualy the front rear one .....but check all 3 ..the one on the front drivers side of the diff is your culprit ..its about a tenner plus vat to buy and listed as a 30 min job .....lr main stealers wanted £88 supply and fit for it ...but it cost me about £14 for a gen lr part and 30 mins of time .....you can easily test if its gone by lying under your truck and pushing the rear propshaft uj where it meets your rear diff up to the underbody of the truck and pulling it down towards the road ...if it moves a lot and doesnt have mutch resistance ....its ****ed !!!!!!! lol have fun