I sent an email to SA transport about a month ago for clarification as I'm leading a group up there, most towing trailers.
I asked about a 4x4 @2•8 and a camper of 1•2 for a total of 4•0 GCVM.
The response was prompt, in summary...
The 3 ton is the total of the vehicle or combination regardless of possible GCVM.
As explained the 4x4 would be OK but with the trailer on I would not be permitted to travel.
As long as when wieghed it must be the under 3 ton figure regardless of possible loads, ie; an empty tray truck.
I heard its $1000 a tyre if caught but have not been able to confirm it and haven't asked SA Transport.
Cheers Kyle.