Chris Williams' Journal

This is close to the text I put as a question on the forum:

I've only put less than 100 mls on the car since the rebuilt and when it came to the rear end, I pulled it down almost completely but didn't do anything to the diff. except drain the oil, pull it out and check to see all the teeth where there. New gasket, new oil and it all went back together after I'd painted it.
The bearings got the same treatment and as they seemed ok and I thought it would not be too big a deal to replace them later if I needed to, so they went back in with new seals and O ring.
Well, I getting an intermittent, 'sort of' grinding noise that is becoming more regular. It's not a 'whine' like a wheel bearing noise and it doesn't seem to make any difference if I'm accelerating, coasting or backing off.
I was able to duplicate the noise with the car on jack stands in 3rd and 4th, high risk, I know and I wasn't game to leave the drivers seat to listen exactly where it was coming from. My gut feeling is the diff.
I made sure the new universals had plenty of grease and I thought I'd check the oil level in the diff while I was there. (actually I was checking to make sure I'd actually put oil in it, I had.)
The oil was a little discoloured, which concerns me a bit. Is there anything in the diff which would destroy itself and discolour the oil. A soft metal bearing or shim rather than a roller or ball bearing which I would expect to 'whine' before failure?

I've decided to replace the wheel bearings and I bought the bearings and new seals today.

Here's the text from the followup question:

Have decided on a plan.
Replace wheel bearings and see if noise goes - without replacing oil seals.
If noise is still there, attack diff.
If noise is gone, replace seals and forget about it.
Question relates to the style of wheel bearings available. Have decided to go with $20 China bearings as opposed to the $50 Japanese bearings.
They have seals both sides and are pre-packed with grease. I sure the old ones didn't, they got there lube from the diff.
Is this a plus or a minus?
Does this make the oil seal redundant?

Got the bearings and seals today for $38.

Checked the receipt from Sportsparts - $11.80 each, just for the seals.
Kind'a makes you think doesn't it?

'Gosford Bolts and Bearings'. These guys are the real deal!