My Ford Ranger 2.5 4cyl. 110K Mi. manual transmission has always been a little stiff sifting. I recently changed the fluid and seemed to improve but now it seems to be getting stiffer into first gear form stop and occaiasional grinding between any gear. No other symtoms like noise or slippage. I am past the 80K clutch replacement standard. I am worried it could be air in the hydrolic master cyclinder or the faulty transmission itself. Any recommendations. Should I get it diagnoised before I pay for a new clutch install.