[turborat]

Here's my .02.

Unless one can see visible damage of the reverse lock-out mechanism, the problem is most likely a misalignment of the shifter linkage. I have found that shifts from 5 to 4 were fine when the box was cool. At temperature the problem got progressively worse. I now get the box nice and warm and and then adjust the shifter linkage. I can now downshift with relative confidence that I will not nick reverse gear once everything is up to temperature.