Never had a problem but every now and then when selecting 1st after sitting in N for a while it crunches. Thought maybe I wasn't pushing clutch in far enough but tried again and still does it.
I know the early ZD30 boxes had a crap 5th gear. I stripped the splines but I was towing at the time, a big no no apparently. It was out of warranty but Nissan fixed it for zilch as apparently it was a known fault. (this box was in a 2000 GU patrol and it wet bang in 2003). My gearbox had a redesigned larger 5th gear shaft put in, which I am led to believe was standard fitment to the later ZD30 gearboxes. I don't know what year they modified the box but it must have been around 2002 or so I think. Having said that the remainder of the box is pretty tough. I was in the middle WA and towed my van back to Adelaide on the remaining 4 gears with no problems at all apart from the rattling gear spline (did drop the oil though to get the copious amount of metal bits out).