Knocking and grumbling

[bamba]

Just after some conformation really on what I think,
car, mk 2 Gti,1.8 valve,1990, standard.
Started hearing some concerning knocking noises, at wheel rotation speed , loudest when off load, or on lock . Also to car has a tendency to pull sharply to one side for split seconds
Sounds similar to a really bad wheel bearing or cv joint problem, was hoping to find a loose drive shaft end nut or drive shaft to flange bolts loose,but everything is ok,When the cars is up on jacks,and running in gear , if one wheel is stopped, it is continually trying to "snatch" and rotate the wheel that is stopped.
I've had one previous diff' failure, which went from , what's that strange rattling noise, to bit of gear box being ejected from underneath in about 30 seconds.
So I'm  thinking the diff' and it rivets for the planet gear carrier are beginning to part company. Car is now off the road to save destroying my clutch.

[gazareth]

if you drain the gearbox oil out you can get right at the crownwheel to check if its loose (see it through the drain plug)

[bamba]

I'll have a look tomorrow,  already dropped the oil to see if there's any debris in there. No solids but very metallic.