It’s a question we hear regularly from operators looking to grow their hydro excavation fleet: can Waimea build an 8x4 hydrovac truck? The answer is no, and it comes down to a deliberate design decision rather than a limitation.
Waimea has spent years refining our Allvac® range , and that experience points consistently to our 6x4 platforms, including the Allvac® AV7000H, as the best balance between payload and manoeuvrability.
Shifting to an 8x4 isn’t simply a matter of adding an axle. It pushes the wheelbase out from our current maximum of roughly 4,500 millimetres to around 5,900 millimetres, a jump in length that directly affects how tightly the truck can turn.
New Zealand’s roads and job sites weren’t built with a longer-wheelbase truck in mind. Between tight urban streets, steep hills, winding rural roads, and confined worksites, a tight turning circle is essential to getting the job done.
A 6x4 Allvac® can work its way into spaces that would leave an 8x4 struggling. Picture manoeuvring a longer, less agile truck through the streets of Wellington or Dunedin and it’s easy to see where the compromise starts to hurt you.
A bigger chassis generally calls for a bigger debris tank, and a bigger tank needs more vacuum power to match it. The AV7000H uses a lighter hydraulically driven vacuum pump. Scale that up to an 8x4, and you need a split driveshaft system, which adds weight and eats into the payload gain an 8x4 was meant to deliver.
Cost tells a similar story. An 8x4 chassis and superstructure both cost more, but the payload benefit typically works out to only two or three extra tonnes - not enough to offset the added cost, complexity, and lost manoeuvrability for most operators.
That doesn’t mean Waimea rules out 8x4 builds altogether. We do occasionally build 8x4 vacuum tankers, a different application where the vacuum system can support a larger tank without the same hydraulic and driveline challenges an 8x4 hydrovac would create.
For hydrovac trucks, a well-designed 6x4 gives most New Zealand operators the strongest all-round combination of payload, manoeuvrability, reliability, and value. A bigger platform can sound like an obvious upgrade, but once you weigh up the trade-offs, it isn’t always the better choice.
