Yeah, diecast for sure- I know they wont last too long, but it'll be a blast while they do
As for size, I dont have an exact measurement, but there is a good picture on page 7 of the manual:
http://www.tamiya.com/english/rc/rcmanual/txt1.pdf
Just to make things harder, they are splined on the inside, so a new shaft with maybe a cross pin to hold the gear in place would be needed- I can foresee that getting rather expensive and complicated with all the tooling and setup required..
I think I'd be inclinded to go with rc4wd.com Kyosho Madforce axles, then get some insides from donar axles/ spare parts etc.
I would have thought though that Tamiya woudl have released a TXT-2 by now- been a long time without a big, straight axle truck from them...
