Good morning all.
Doubts have been clarified with a photo of the transmission label received from my nephew (below).

[Linked Image]

The actual Hydro-Gear transmission in my nephews Kubota T1770 is a K1082-11111 model 315-2000, being one of the GT-2000 series models. :-)
Have now sourced the specific exploded parts diagram for the 315-2000 and am waiting on Scott (nephew) to call in and advise which gear (or gears) is the one that he has broken.
The parts I think he needs for the 315-2000 are the same as the 311-2000 and are available from the USA.
Until Scott verifies the part, there's not much I can do to see if I can get them here in Oz.
Thank you for your assistance, and have a great day.

Environmentally friendly recycling at it's best