It sounds like a quite a heavy knock similar to the chatter of anti roll bar link but heavier, if that makes sense.
Slight play in the osf anti roll bar link when I got the van, so replaced it with a good quality one, noise still there.
Many times on the axle stands at home showed no play in anything when worked with a pry bar.
Anti roll bar bushes had no play but looked past their best, replaced, noise still there. Noticed when replacing these bushes that the osf one doesn't clamp the roll bar at the bottom (bush doesn't close up)so I replaced the clamps for the bushes, noise still there, gap still there, made an additional mounting plate for the roll bar to sit on and close the gap on the bush, gap closed, noise still there.
Wishbone bushes don't look in the best condition and cheap to replace so I replaced these too, noise still there but the wheel wobble at 60mph had now gone, thats another story though
Ball joints were new when I got the van so ruled those out. Noticed it was worse when the wheel was dropping into a pot hole or off a speed bump. Whilst servicing the other day and wheel just resting on the floor (very little weight on the wheel) I tugged at the strut and I had a small bit of play, hmmmmm, check the other side, which is quiet, no play. Found a used strut on eBay complete, fitted and hey presto, quiet. On checking the old strut, the top mount had a small amount of play and the rubber bonding cracking. So if you have a knocking noise check your top mounts, lots of searches brought up anti roll bars but nothing else. I am a mechanic so no labour charges, plus a mountain bike habit so everything is on a budget otherwise I'd have just chucked new strut assemblies on.
Hope this helps someone.
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