Not too sure about this one Mel, as unfortunately, I never got to work on a 757. Do the 535's have mid span shrouds? It was the presence or absence of mid span shrouds that generally established whether we tied the fans or not.
On the RR
's and P&W's, we generally did tie the blades when we were working on the engines, as the noise of the clappers hitting was very annoying. The GE
also had mid span shrouds, but for some reason, the blade set fitted together much more tightly on the CF-6 than either the RR
or P&W, so we rarely if ever tied the blades.