Thanks Guys,
It worked. I un-installed NI-SYNC and physically removed the 6653 from the chassis.
I then re-installed the file from the link you provided. This re-install removed all drivers for all PXI modules in my chassis. That was ok, all I had to do was re-install all of the drivers for each one.
After a re-start and physically re-install the PXI-6653, the NI_SYNC sub-vi's were on the function pallete.
Thanks,
Roger