A few weeks ago I was convinced by posts here suggesting that there's no mechanism for reverse gear lock-out (when moving forwards) in the Aisin
6sp gearbox. IIRC there was a link to miata.net posts implying the same- that reverse gear lockout is a myth. I also checked the 6 speed box FSM, and can't see anything obviously there to show that a lock-out exists. So about 10 minutes ago, I tried it out - very carefully at first. There is in fact a lock-out. I can get the shifter across to the right into the horizontal part of the gate, but it won't budge down towards reverse at all when you're moving forwards. There's no way to accidentally engage reverse say if changing from 3rd directly to 6th. My NB is '98 production JDM VS 1.8 RHD. Perhaps this is not in all NB 6 sp models. Cheers.