New information that could reveal the location of the remains of missing Sydney teenager Trudie Adams has been uncovered in an ABC investigation.

The Barrenjoey Road investigative team has been told the 18-year-old's remains could have been disposed of in a waterway near Christmas Tree Hill at Cottage Point, in Ku-Ring-Gai Chase National Park.

Adams vanished after hitchhiking home from the Newport Surf Club on Sydney's northern beaches in June 1978.

The Barrenjoey Road team has been investigating Adams' disappearance in a three-part ABC TV documentary and a true crime podcast series.

The information discovered by the ABC has been provided by a former law enforcement source.

According to this source, a known underworld figure on Sydney's northern beaches called Guido suggested that Adams' body was disposed of at Christmas Tree Hill.

The ABC understands this location was not included in the extensive search for Adams' body in 1978.

NSW Police have told the ABC that land and water searches had been conducted in various areas of the Ku-Ring-Gai Chase National Park over the years, as well as surrounding areas.

The Barrenjoey Road team understands that Guido, who is now dead, worked at a Brookvale smash repairs shop in Sydney's north and was also known to dispose of dead bodies.

Do you know more? Contact unraveltruecrime@abc.net.au

The main suspect in Adams' disappearance is Neville Tween, a safe-breaker, drug dealer and convicted sex offender, who died in jail in 2013.

One of Neville Tween's close associates, a convicted criminal called Gary Batt, also worked at a smash repair shop in Brookvale.

The new lead has been passed on to NSW Police's cold case unit.

The final episode of the three-part investigative documentary series, Barrenjoey Road, airs tonight at 8:30pm on ABC TV and iview.

To follow Unravel's ongoing podcast investigation into the disappearance of Trudie Adams, listen to Unravel Season 2 online, on the ABC Listen app or wherever you get your podcasts.