Weird knocking noise under XJ

OK, I'm a little stumped on this one ...

Pulling into my subdivision this morning and I hear a rattling/knocking noise in the XJ going in a straight line ... Sounded exactly like the pinion yoke or tcase output was hitting something ... Went on until I tapped the brakes and now I can't make it do it again. Nothing looked loose or out of place when I looked and everything seemed tight.

The front shaft is out so it's not a front shaft ujoint. Sounded like it was right under my ass.

Any ideas? I'd tear into it right away but my 2yr old has other plans until nap time.

2000, AW4, 231 AA SYE, ~5.5" front lift.

Sounds like your caliper was loose. Or a warped rotor.
When you hit the brakes and it goes away, they are the first suspect. IMO

I was thinking caliper but the noise was a new one to me. Just tossed in the front driveshaft quickly, hoping I could get it to happen again if the front driveline was spinning. Sometimes my kids let daddy play too
I'll give the caliper bolts a snug just incase though .... So close to the WJ swap I don't want to have to redo the stock front brakes just to get to work (that and I just replaced the works about 4 months ago). I did notice the front knuckles had minor divots on the insides though. Big issue is the 250km trip to work tonight and then back again next week. Figures though, she's been too good for too long, must be getting cranky.

Thanks
Dave

Mine have the same grooves in the knuckles as well. And make the same noise you describe.