Differential/Drive Train Noise

[66CudaFormulaS]

I have a 66 Barracuda with an automatic and 7-1/4" differential. I am getting noise when between throttle and coast. ie: On the gas, no noise. Completely off the gas, no noise. Anywhere in between it "sings" Any ideas as to whether this is a differential issue, or some other component? The universal joints don't seem to have any slop in them.

 

[briankaplan]

"Sounds" like it's time for a complete rear axle overhaul.
Gear noise on coast. Is the mesh of the gears worn. Check on
new gears and bearings.

 

[busted knuckles]

I had a similar sound in the same circumstances. The pinion nut became loose. Give it a look.