GNs-r-slow you beat me to it twice.

All T5's use ATF NOT gear lube! Rule of thumb....if the tranny use's carbon lined synchros (t5, t45, t56, 3650) its uses ATF if the tranny use's brass snychros it takes gear lube (3550, tko's)

Might be the input and/or output shaft bearings making some noise. Tranny's are hard to diagnose with out taking them apart usually. I would keep an eye on it, its probably getting towards the end.