Name that noise

[jamesban]

All of the diff gears were brand new although I dont think they were hardened just stock replacements, I built two new diffs with HD cups and they seemed very smooth after assembly, the center diff was locked with what looks like hot glue and I left it like that. The drive shafts and axles all appear straight. Im honestly not sure what it is. I had a similar noise in my brushlass e-savage when the stock plastic trans blew apaprt from the 9XL motor runnig on 6 cells. Other than that I never heard a noise like this. It doesnt sound like metal diff gears grinding to me? I may have to wait till soemthing fails to figure it out or if the slipperential makes it go away?