A koala has been released back into the wild after enduring a 16-kilometre nightmare clinging onto the axle of a four-wheel drive in the Adelaide Hills.

Don Bigham, from Fauna Rescue South Australia's Koala Hotline, said they believed the marsupial crawled into the wheelwell where it attached itself to the axle last weekend.

The koala was seated upon the axle as if it was fork in a tree. ( Supplied: Jane Brister )

It then found itself being driven for 16 kilometres through winding, hilly terrain. The driver was reportedly flagged down by other motorists but failed to find anything wrong.

It was not until he stopped that he heard crying under the car and called the Koala Rescue Hotline.

Fauna rescuer Jane Brister went to the site and initially tried calling the RAA.

The Metropolitan Fire Service responded and had to remove the 4WD's wheel as it was a new car and the driver could not find the wheel lock.

"I suspect the fireys may have used some very subtle engineering, but anyhow, the wheel came off," Mr Bigham said.

"The koala was taken into care and apparently it came out of all this very healthy, surprisingly so.

Ms Brister said that even though she knew what to expect it was still a shock to arrive and see a koala wedged inside the wheelwell seated on the axle as if it were a tree fork.

"I could see her behind the wheel but I had no idea, until we got the wheel off, whether she had broken limbs or what the story was," she said.

The koala, pictured here recovering, came out of the ordeal uninjured. ( Supplied: Jane Brister )

"She'd been crying, was very distressed and was in shock for 48 hours."

It was while rushing the koala to the vet that Ms Brister found a sad element to the story.

The koala was lactating and had knotted fur on her back — signs she had been carrying a joey.

Ms Brister went back to the site and searched for the joey for two days but to no avail.

"After everything she went through, she lost her joey as well."

A history of strife among vehicles

Mr Bigham said it was not unusual for koalas to get "themselves into strife with vehicles".

He referred to the case of so called "Bear Grylls", an Adelaide Hills koala that survived being hit by a car at 100 kilometres per hour.

It became stuck in the car's grille and was not discovered for another 10 kilometres later when the driver arrived home.

"We've had people think they might have hit a koala, really looked around the car and not being able to find it, and then driven off somewhere but eventually hearing noises," Mr Bigham said.

"One person heard noises coming from within the engine compartment. The koala was sitting up there somewhere and I think that one was okay as well."

The latest koala climbed into a fork of a gum tree on its release and promptly went to sleep.