Hi Shifter
The serial number for the transfer case is usually on the rear face at the bottom, just below the fill plug.
Even if it is one of the transfer boxes that pre-dates the LR fix up, I wouldn't panic just yet, there are other things that can cause clunks in your drivetrain without it being the mainshaft wear problem.
The first to check is the rear A arm ball joint. This is located on the top of the rear diff and will cause clunks when it is worn. Also check the rubber bushes at the chassis end of those same arms. Best thing to do is get a big screwdriver or small pry bar and see if there is and looseness or deterioration in the bushing. While your under there, you might as well check things like the propshaft uni joints and splines to see if they have a lot of slack too. Try all these first before you worry too much about the transfer box.
Paul [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img]
