Atinae Afamiliona, 50, has been in custody since the attack in the southwestern Sydney suburb of Minto, on August 29 last year.
The couple, who have grown children, was driving home around 10.30pm when they began arguing about their relationship.
He later told police his wife had "hurt" him by saying she no longer loved him.
Mr Afamiliona, who was behind the wheel, also suspected his wife was having an affair and blamed her for what was about to happen.
He immediately pulled the car over and Ms Afamiliona got out and tried to hail a taxi.
When he restrained her, she allegedly scratched him and he removed a machete from underneath the driver's seat and attacked her.
As he rained at least ten blows down upon his wife with the machete, Ms Afamiliona held up her hands and arms to protect her face.
She then tried to crawl under the car to escape him, but he continued to hack at her exposed legs.
Ms Afamiliona suffered four severed digits, as well as lacerations to her calf and ankle.
Her husband then drove her to Campbelltown Hospital where he dropped her off at the accident and emergency section and then returned home.
She was transferred to Liverpool Hospital in a serious but stable condition.
Police charged Mr Afamiliona with assault occasioning grievous bodily harm and issued an AVO against him.
His lawyer Kieran Ginges told the District Court on Friday that his client had immediate remorse about his actions and the attack had been "spontaneous" and not premeditated.
Prosecutors told the court Ms Afamiliona was extremely dependent on her husband, who had previous violence-related convictions.
"The letter can be seen as a symptom of being caught in a cycle of domestic violence," Bernadette O'Reilly told the court.
Atinae Afamiliona will be sentenced in September.
