Police established Strike Force Arapaima in April to revisit the cases of Robyn Hickie, Amanda Robinson and Gordana Kotevski.

Ms Hickie, then 18, left home about 7.15pm on April 7 1979 and was spotted at a Belmont North bus stop a short time later.

She has not been since.

Her disappearance came two weeks before 14-year-old Amanda Robinson was last seen at a Swansea bus stop after attending a dance at her Gateshead high school.

Ms Kotevski, then 16, was last seen in 1994 when she was forced into a vehicle on Powell Street while walking from Charlestown Square to her aunt's home on the same street.

A coronial inquest into the three disappearances found the trio had died, most likely as a result of foul play, but extensive investigations over decades have been unable to find any trace of them.

On Monday police released an image of a car they described as a distinctly green mid-1970s four-door Holden Torana sedan.

Investigators believe the vehicle may be linked to Ms Hickie and Ms Robinson's cases.

Lake Macquarie Police District crime manager Detective Chief Inspector Greg Thomas said the car was a "significant" new lead.

"We are hoping anyone who was living in the Lake Macquarie region in the late 1970s may have a recollection of this Holden Torana, in particular in the month of April 1979," he said.

"We understand it's been 40 years since Robyn and Amanda's disappearances, however, we are seeking assistance from anyone who may even have moved to a different state or who may have some memory of this vehicle to come forward to police - you can remain anonymous through Crime Stoppers if you wish.

"It may seem like small or insignificant information from decades past - but it could help investigators solve these cases."

The families of the three missing women have requested privacy, police said.

Strike Force Arapaima inquiries continue.

Anyone with information is urged to call Crime Stoppers on 1800 333 000.