Steering "clunk"

I am having a problem with my steering, I think the gear box in a 2000 SE with approximately 80K miles. When I turn the wheel to the left I get a "clunk," which seems to vary in intensity based upon my rate of acceleration/decelleration and speed of turn. The steering linkage is Currie's HD system and is only about 4 months old, the suspension is RE 3.5" superflex, and I am running 32X11.5 MTRs. All three mounting bolts for the gearbox have been torqued to spec, and I don't have any play in the pitman arm.

I found a previous thread from years ago for the same problem but there was little input into problems/solutions and instead drifted into discussion about play in TREs/linkage, which I don't have. I don't have a steering box brace, and have no signs of cracking around the box, but am wondering if this is a precursor to the porblems that this might fix? Problem with the steering box itself? Something else? Ideas?

Have you removed the box to see behind it?
It cracks out there, as well.
The bottom part of the frame is where it usually cracks out.

No, I haven't removed the box yet b/c I wasn't sure if that was the culprit...is it common for cracking of the frame to cause a "clunking" noise when turning (only to the left)? Is it possible that the box itself is failing or is that unlikely?

Yes, it's common for a crack to only clunk when turning one direction.
It might also be the box, but cracks are hard to see up there behind the steering gear.

Great, I'l check that out...thanks.