Hello,I have finished rebuilding a 1964 PV544 with M40 transmission.On dismantling this I found the three small plates on the 3rd/4th gear synchro along with the two circular springs lying in pieces on the bottom of the gearbox...no doubt there was a problem.Otherwise the gearbox was fine so I replaced these with some from an Amazon gearbox (that worked OK) along with all bearings.Synchro rings were OK. After 100 kms when the restoration was over, I could not engage 3rd gear at all,other gears shifted fine. After much effort,3rd gear engaged and locked...So I had no other option than dismantling the gearbox again. I found these three blocks to be out of their place and thus not allowing 3rd/4th engaging sleeve to move correctly. They had not been damaged,though so I put them back with the circular springs in the correct position,as stated in the manual.To be 100% sure I fitted the whole 3rd/4th hub/sleeve assembly from the Amazon gearbox,even though I did not notice anything suspect on the original hub/sleve assembly. After driving the car another 200 kms,I experienced again difficulty engaging 3rd,other gears engaging fine again. Gear lever has no slop, gearbox oil is correct,clutch may need a minor adjustment,I will check again,but does anyone have an idea what else could be causing this? Did you,in particular,ever have experience with 3rd/4th locking blocks slipping out of position? Is there a way to determine if there is wear between the hub and the sleeve splines?
Also,for anyone trying to fit a radiator shroud on a 544, I fitted one from a Suzuki SJ413,it needs only two cuts to clear the steering box and drain plug and fits nicely.