Short version? It did.
I checked in the owners manual what oil I should put in and I was pretty confident that I was looking at the right gearbox as some of them in the book have different specifications. By the time I'd drained the oil I was starting to get a nagging doubt so I checked the builders plate and compared that to the number in the book.
Guess what? I'd gotten the wrong oil. The gearbox I thought it was used the same oil as the engine which is due to be changed soon anyway. But the gearbox it actually is needs SAE 75W-90 GL3. Definitely not engine oil. This was about 1625 on a Sunday afternoon so I took the other car around to all of the parts stores in town and by the time I got to each of then they were shut. One shutting just a few minutes before I get there even.
So what to do? Where else can I get a bit of a specialty oil? Servos that cater to trucks and have a bit more range than just fuel and chips. I managed to find the 3L I needed at the servo just out of town for about $80 total. So pretty expensive for something that I thought I already had.
The astute among you will note that the spec. calls for GL3 and the picture shows GL5 oil. When I found the oil I had to pull out my phone and do a quick search to try and find if they are compatible. I ended up finding the answer on a scooter forum which indicated that GL5 oil will be fine for a GL3 spec.
After sorting all that out I made it back home to re-fill the gearbox. I ended up putting in between half a 3/4 of a liter more oil in than came out so that may have had something to do with the bad shifting. Any by guesswork and feel I finished as the sun had pretty much gone down.
Then I went for a drive. While not being silky smooth by any means. The gearbox now shifts reliably into 2nd and feels like you'd expect the gearbox on a ute to feel.
I think I've talked too long by now so I'll finish here. But remember, triple check specs before the shops close.