Despite knowing the Mitsubishi he was driving was not roadworthy, the defendant attempted to overtake the Toyota in front, which was being driven by Sami Veikoso.
Mr Manu was in the passenger seat.
Tualau clipped the vehicle as he passed, causing it to mount the kerb and veer left into a tree.
Judge Field told the court the driving conditions at the time were wet and both vehicles were exceeding the 50km/h speed limit.
Mr Manu sustained serious head injuries and was rushed to Auckland City Hospital. He died in the critical care unit two weeks later.
Mr Veikoso was also charged over the incident but police yesterday indicated the charges would be dropped.
Paula Kohinoa, managing director of Soni Contractors where the men worked, dismissed the two drivers after the crash but it was revealed in court that he knew about the defects in the truck Tualau had been driving.
"Just why he allowed you to be driving is quite beyond me," Judge Field said.
Mr Kohinoa could not be reached for comment.
Mr Manu's funeral had cost his grieving wife, Veisinia, more than $11,000 but the judge said it was unrealistic for Tualau, who had three children and a wife to support, to pay all of it.