I've changed differential once and 6spd twice, the last time I put Pennzoil synchromesh in the transmission I got slightly better results. My car has 52k and I've heard the more miles the better it shifts.DO NOT DRAIN FLUIDS UNTIL YOU CAN BREAK LOOSE THE FILL PLUGS !!! you will need a 14mm & 17MM hex socket 1/2" drive I used 5/16" ID diameter plastic tubing. stuck one end on the bottle and the other in the hole. Have you changed all the brake fluid , the clutch & slave share the same fluid as the brakes. Not too hard
14mm & 17mm