[Rick 427 Cobra]

YES! A friend and I went round and round over this issue some years back. Fluid levels and types of fluid had no effect. The cure is some jag covers do not have a shield inside the cover to protect the vent from splash. Its a simple piece of sheetmetal, but thats the cure. Drain the diff and remove the cover. I think you will see a bare hole. I will try to find a picture to help illustrate.