So I just joined and I have the same 3rd gear crunch issue. 4-3 2-3. I changed the oil to Mt90. Same problem but the shifting is definitely sweeter. I took the car for a 35 minute drive no improvement. If I shift below 29 mph no crunch. If I gently coax it in,I sometimes may get lucky. I have resigned myself to the fact that its the synchro. I will try to live with it until a clutch change is due unless I get fed up and can’t take anymore.