Strange Syncro axle noise - any ideas?

[RJES]

My Syncro has developed a strange noise at axle speed. It's a dull thud sound once per turn of the axle, which gets louder under load. Steering angle makes no difference, and it continues quietly under breaking. It doesn't sound like any wheel bearing or CV joint I've heard before.
I stopped using it almost immediately (it's expensive sounding!), and have only done a few checks so far. I thought I'd see whether anyone recognises the symptoms though.

I took the propshaft off, and checked whether everything turns freely with all the wheels off the ground. Everything seemed normal.

I then drove it with the propshaft off, the theory being that the noise would continue to get louder under load if it's coming from the rear, but not if it's from the front. There was no change with the propshaft removed, so I assume it's coming fron the rear.

I did find slight play in one of the rear wheel bearings, but it's rather an odd noise for a wheel bearing, unless it's falling to pieces. However, it all turns smoothly. All attempts to remove the hub nut have failed so far. One bent 3/4" breaker bar! Time for a decent one rather than unbranded junk....

Thanks for any help.

[toomanytoys]

Wheel speed...
CV joint,
diff, maybe chipped tooth

Checked no tyres have an "egg" or something lodged in the tread?

[RJES]

I'm hoping it's a CV joint (even if it's a front outer!), and really hoping it's not a broken ring gear.....

[RJES]

I spoke to Aidan today, and he suggested the diff bearings, and checking for play by looking for movement at the CV flanges. It'a a scary, expensive thought (if they've gone, no doubt the R & P have had it too), but a check it never occurred to me to do whilst I was underneath. I'd have had a look today, but it's not stopped raining.