Expert witnesses are raising new questions about the death of a 32-year-old father 17 years ago, in a rare second inquest into the case.
Eddie Tavinor died while driving on Auckland's Southern Motorway in 2000, when part of a passing truck's drive shaft came loose, crashing through his window.
An inquest into Tavinor's death took place in 2002 and at the time, experts agreed mechanics servicing the truck days before the crash critically failed to notice wear and tear on the drive shaft.
No charges were laid in 2002, but the case piqued the interest of engineers Timothy Smithson and Peter Morgan, who started their own investigation.
The pair are giving evidence to the second inquest, claiming that many hauling vehicles on Kiwi roads have a design flaw in their gearbox.
The pair say they have seen the same gearbox failure many times since, but never with such fatal consequences.
Several experts in the haulage industry have been called to give evidence, with some arguing that this new theory is simply wrong.
"I have not been aware of any problems with the design of the relevant types of gear boxes, or their use in Mitsubishi or other types of trucks," said TR Group National manager Peter Irwin at the inquest.
Mr Tavinor's family are attending the inquest, which is expected to last up to a week.