Flights Pretoria to Durban
Interlink Airline was the only airline operating flights from Pretoria to Durban, until it suspended flights when it went into provisional liquidation on the 23rd Feb 2010. Options include flying from Johannesburg to Durban, or taking a coach (like Translux).
Coach trip
The Greyhound & Intercape operates coach trips from Pretoria to Durban.
Car rental at Durban International Airport
Here's a list of car rental options at Durban International Airport: