By Megan Hickey

CHICAGO (CBS)– A defect has been causing issues for thousands of Nissan owners, but the models in question have never been recalled.

Rich McMurray’s $6,000 problem started with a flashing overdrive light on his 2007 Nissan Xterra. Once he took his car to be checked, he said he realized a “nightmare of a problem.”

McMurray’s transmission was shot. He took the car to several shops and got the same diagnosis: A defect with his radiator had allowed antifreeze to mix with transmission fluid.

“That eventually clogs the filter and the car stops moving,” Michael Balachowicz, owner of Chicago Transcraft, said.

Balachowicz said he gets frustrated that Nissan owners, like McMurray, visit his shop for this exact problem regularly.

“It’s a known failure,” he said.

The affect models include 2005 to 2010 Frontier, Pathfinder and Xterra vehicles.

“It lets the transmission fluid mix with the engine coolant and that’s death for a transmission,” Balachowicz said.

The cars have a price tag of anywhere between $3,500 and more than $6,000. So many Nissan drivers complained that NHTSA launched a defect petition review and received more than 2,500 complaints.

Of those complaints, 638 had to do with to safety concerns like stalling engines and vehicles that are unable to maintain speed.

But the NHTSA concluded that since the majority of the complaints were not classified, a risk to safety they would not order a full investigation or recall.

Meanwhile Nissan extended the warranty on those cars, telling CBS2 in a statement that the extension was granted “in the interest of customer satisfaction.”

McMurray’s car doesn’t fall in the warranty window, but even if it did, the deductible for more than eight years or 80,000 miles can be over $2,500.

“I feel they should have recalled everything and fixed it properly instead of extending the warranty and maybe cover a few of them,” McMurray said.

Balachowicz said a preventative fix only costs about $200.

On Monday, a Nissan spokesperson reiterated that the issue was not deemed a safety risk, nor was it considered for a recall. Nissan sent notification letters to more than 850,000 potentially affected owners.

Megan Hickey