Originally Posted By: unDummy
When compared to DexronIII, ATD is thicker!
I would definitely top off that diff immediately at another shop. If it was very low, then you risk some lube starvation issues and that will explain the whine, along with future diff failure.
Or, the whine was noticeable before and someone filled the diff with some gear oil to hide it in order to dump the vehicle.
I highly doubt that DexronVI is a culprit here.
I would use ATF+4. Its thicker the DexronVI, should help mask the whine, and doesn't shear as quickly as regular DexronIII's.
How about Mobil's syn ATF or Valvoline's Mercon 5. They both claim to be Dex 3 compatible.