Whilst driving on the highway at approx 65mph there was a clunk from under the car, followed by lack of acceleration, smoke was coming out from under the hood. We were unable to pull onto the shoulder immediately due to highway construction. We eventually pulled over and stopped the vehicle. We immediately popped the hood to check the source of the smoke and there was a fire coming from behind the engine with visible flames. The flames were burning and we could smell a strong chemical / oil burning smell. Fortunately we had a fire extinguisher and extinguished the flames quite quickly. We were towed off the highway and our insurance then towed us home. On inspection it was determined that the transfer case (PTU) had failed causing a catastrophic failure and a fluid thermal event caused by pressurized, superheated oil directly spraying onto the scorching exhaust pipe sitting right behind the engine block, triggering the immediate underhood fire. There were no warning lights on the dashboard and the car had been meticulously maintained. As serious PTU failures are common in 2015 Jeep Cherokees, I reported this immediately to Jeep, they sent a technician to inspect and he confirmed that the transfer case had failed, causing a fluid leak ignited by the hot exhaust. There are no recalls attached to my VIN and I am fighting with Jeep/Stellantis for a repair since this is a known and acknowledged issue across this model. I had the vehicle towed to the Jeep dealership on instruction