Is there any recourse if my GX is out of warranty and I need the dreaded clunk fixed?

Have you taken your GX to a Lexus dealer to have the problem diagnosed, done the appropriate groveling and been refused?

I'm not sure I've seen a pattern on when Lexus will fix a TSIB problem on an out of warranty car but they seem more flexible if the warranty has expired fairly recently. If you can't get Lexus to fully fund the repair, you could try to get them to split the cost.

Try calling Lexus headquarter and complain and bet Sometimes they will do a good will TSB.