Squealing noise when foot off accelerator in lower gears 2007 volvo d12

I have a 2007 volvo d12. I am getting a squealing / squeaking noise from the rear when i take my foot off the accelerator in lower gears (1,2,3). It also shows up when I am in gear downhill. A mechanic inspected my truck and he said my break pads and driveshaft looks good. He said it was just probably worn out rubber inserts that are placed at the end of the spring. On my truck, they are small yellow colored inserts. Does any one have any idea what it might be.