Need some ring & pinion help

[Georgia Mike]

OK I need some help here. It's been about 5 years since I set up a diff, and the only other one before that was 3 years prior, so it's obvious I'm not a pro.

I'm trying to determine the source of the rumbling coming from my 8.25" rear. From what I read on Randy's R&P site, my symptoms mimicked worn carrier bearings, but upon inspection I'm thinking it was just a botched setup (symptoms are no noise until around 20 mph then I get a low rumbling noise, whether under acceleration or coasting) I did find a lot of metal shavings, so I know whatever I have going on, it's not good. I measured backlash and got a fairly loose .015", but I have zero side to side play on the carrier.

Here's what I have, and again I'm no pro so I can't just compare to a cartoon chart and say "yeah that looks fine" or "holy crap I can't believe that thing hasn't melted down yet!"

Coast side:


Drive side:


Quickly ran a magnet through the gear oil in the pan, this is what I found:


Hard to see, but as close as I could get to see the wear pattern on the drive side:


Wear pattern coast side:


After handling the carrier pin this was left on my fingers:


I looked inside the Detroit and could see no obvious damage, but I wouldn't expect there to be that would cause the noise issue I'm having.

:helpme: Any help out there?

 

[Lowrange2]

I'm no pro either but I've never seen that much contact in the pattern.

Last time I had an obvious rumble at speed under acceleration was due to bad pinion bearings.

 

[Georgia Mike]

Well that's the thing. As far as I can tell the noise is there no matter what after ~20 mph or so.

 

[Georgia Mike]

I'm thinking that the pinion is too high and they tried to compensate for it by pushing the carrier away from it. Either that or the big backlash number is just a product of wear, which would explain the metal in the oil.