NP/NV242 TC 99/00 differences?

I have a '99 with 4.0, AW4, and NP242 TC. My TC is making noise and metal in the oil, so I think it's time for it to go by by.

I have a line on a 2000 242 TC but I'm not sure if it will work in my '99. The parts catalog shows P/N 5209889 for '97 -'99, and P/N 5209899AA for the 2000. Does anyone know what the 'AA' would mean? Any differences in the '97 thru '99 242 TC vs. the 2000 242 TC?

Any 1996-2001 XJ transfer case will interchange.

Thanks.

They added the 'AA' to part numbers when they changed the numbering style.