McLaren has managed to bring the two gearboxes that overheated dramatically at the Singapore Grand Prix "back from the dead", despite fears they had suffered catastrophic damage.

Jenson Button and Fernando Alonso were forced to retire from the Marina Bay race last month after their gearboxes suffered excessive overheating far beyond their design limits.

In fact, in McLaren's history, no gearbox has ever experienced such high temperatures and survived.

Debris cause

Motorsport.com has learned that the overheating was caused by tyre rubber debris and fallen leaves blocking the gearbox oil cooler, meaning that temperatures began to climb.

As the gearbox oil heated up, the heat became so high that it reflowed the solder and aluminium components inside the electrical sensors, meaning that the engineers were racing ‘blind’ without data to monitor the escalating temperatures.

Consequently, the decision was taken to retire both cars on safety grounds, rather than suffer costly on-track failures.

Factory miracle

Although it was feared that the damage had been so considerable that the gearboxes would have to be scrapped, McLaren has discovered that there were minimal consequences

McLaren’s acting CEO Jonathan Neale told Motorsport.com: “When the gearbox operates at those sorts of extreme temperatures, you start to see some pretty catastrophic degradation of the internal components: the steels start to soften, and the gearbox teeth start to break.

“At those temperatures, you also start to see the internal bulkhead glue joints begin to fail, and the carbon starts to degrade and lose its structural properties.

“But we have discovered that the gearbox casings had survived intact, despite experiencing temperature surges more than 45 percent higher than they’d been designed to sustain.”

Highest ever survivable temperatures

Neale reckons that the fact the gearboxes survived was testament to the work of fuel and lubricants supplier ExxonMobil in delivering oil that minimised damage.

“It’s an incredible testament to ExxonMobil and their gearbox oil that we were able to return to the factory, inspect the gearboxes, run them on the dyno, and discover that they’d suffered no functionality issues whatsoever,” he said.

“When you take into account the loads inside an F1 gearbox and the fact that most of the time the oil is just a mist with the merest thin film on the shields, it’s a credit to Mobil’s technology.

“The gearbox team looked over our historical data, and those casings endured the highest-ever survivable operating temperatures we’ve ever recorded, yet they were run on the dyno with functionality identical to a brand-new casing.

“We really brought these gearboxes back from the dead – and that’s unbelievable.”