I had the same problem with a 91 Vmax. The final gear drive assembly was making a horrible sound when decelerating. Somehow the nut holding the pinion gear was not punched in to lock it so in time it loosened stressed the gear and it finally sheared. I checked all over (I'm in the Philippines) but no one sells the final gear only, one has to buy the final gear drive assembly (used ,for about 350US$).
I took the final gear drive to my favorite machinist (the guy does excellent work) and he took the gear out (after fabricating a special tool) put the gear in the lathe, tapped in a thread into the final pinion gear and implanted a new bolt of the same size and machined to the original specs.
After reassembly, he made sure the nut was properly punched in.
I installed the implanted final drive to the VMax, added gear oil, presto problem solved. The machinist charged me 10US$. (Labor in fairly cheap here.) The machinist later told me he had done this procedure before with another VMax.
