just been to the gearbox re-con guy, he's been rebuilding boxes for along time and says to use cheap tesco semi-synth 5W 40 to stop the synchro's busting as they need the friction whats that all about!!!
get a different gearbox guy
I use NFJ
The NFJ is specifically designed for Renault J series boxes EG. JC5, however the face values are pretty much identical so it won't make any difference. I use NFP 75w-80 and its perfect.