Differential noise Options

[Archie]

Hi everyone,
I hope somebody can help with this, but I seem to have a problem with the diff out of my '72. The trans is out of the car so I can turn the axle shaft flanges by hand and they're as smooth as can be, but when I turn one flange and hold the other flange steady, it feels "rough" and sort of makes a "grumbling" noise. Any ideas what that might be, please? Thanks.

[Superhawk996]

I don’t think there is much that can be inferred from the video.

First is that the transmission doesn’t operate in that position. I suspect you don’t even have oil in it? Does it have oil in it?

Even if it did have oil (and not leaking out the input shaft seal and the vent) the oil is not in the right place. It will have drained off all the proper gear and bearing surfaces due to the vertical orientation. Likewise when spun, it’s not picking up oil out of the oil bath properly to distribute back to the gear sets and bearings.

In the first video, then only thing I think I hear is a dry gear set spinning when you hold the output flange.

I’ll gladly defer to Doctor Evil but would want to see what it does with it oriented horizontally, properly filled with oil. I suspect having oil on gear teeth will likely quiet it right down.