I have a 99 f150 with 135000 miles on it, I started noticing a bouncing in the back end when I was slowing down. It would bounce around 40mph. Now ive started noticing a vibration around 35 to 45mph and I can still feel the bounce when I start to slow down. Ive read on the forum about transmission problems causing vibration so I tried putting the truck in Neutral while I was moving and I can still feel the vibration. If it was a transmission problem would it still vibrate in neutral? I dont really have the money to just put it in the shop and tell them to find whats wrong so I was hoping to narrow it down some. Anyone have any ideas?