Whining Noise On Decel

ford put a new tranny in my xlt 4.6 v8 they i got the truck back and now i hear this high piched noise coming from under my seat i think. only on decel and its intermittent. the truck has been back to ford for 3 weeks. they tell me theres nothing wrong and it could be a final drive noise. is this true? because it never made this noise before. please help this truck has been in the shop more the i owned it for the same problem.