Synthetic gear lube in high mileage tranny?

[sixtyfour]

Hey guys, what do you all think about putting synthetic gear lube in a 4 speed tranny with 110,00 miles on it? When I get on it and shift at higher RPM's I get a little grind, nothing major. I'm thinking the syncros are probably a little worn. I know it's a no no when switching to synthetic on a high mileage motor but I think trannys would be a whole different animal? Was thinking of going with something like Royal Purple or Redline, something along those lines...