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.

[Dr Evil]

When you spin one axle the other turns opposite due to the spider gears in the differential doing their job. They aren’t moving more than the output flange on the other side. When you either impeded one axle, or rotate both in the same direction you are now moving the actual differential. This moves the pinion, which moves the rest of the gear stack. Even in neutral, there should be some resistance and noise as you are slowly moving all of those components. What I can’t tell you based on your description is if the amount of noise you are getting is Normal or not. Also, it’s difficult for me to describe normal or not in words.
Why is the trans out? Did it have problems? If so, what were they?

There is precious little you can diagnose with the trans just sitting there and not torn apart. Pretty much only major catastrophic stuff like broken gear teeth, seized stacks, sheered roll pins, stuck in gear.

[Archie]

When you spin one axle the other turns opposite due to the spider gears in the differential doing their job. They aren’t moving more than the output flange on the other side. When you either impeded one axle, or rotate both in the same direction you are now moving the actual differential. This moves the pinion, which moves the rest of the gear stack. Even in neutral, there should be some resistance and noise as you are slowly moving all of those components. What I can’t tell you based on your description is if the amount of noise you are getting is Normal or not. Also, it’s difficult for me to describe normal or not in words.
Why is the trans out? Did it have problems? If so, what were they?

There is precious little you can diagnose with the trans just sitting there and not torn apart. Pretty much only major catastrophic stuff like broken gear teeth, seized stacks, sheered roll pins, stuck in gear.

Hi Doc,

The trans is out of the car as I've just replaced 1st/2nd/3rd synchros and dog teeth (with the help of your DVD!) as - typically for a teener - the shift in those gears was diabolical! I sloshed about a cupful of 90 Gear oil into her to keep things oiled, as the car's waiting for paint and I don't know when she'll be back together.

I'm trying to post a movie clip illustrating what the problem is, but my cinematographer isn't on form these days! Please watch this space.