WADR, I beg to differ. On a very fast track like Mosport where I get a 93.3 mph average lap speed the heat build up is phenomenal. With no exhaust wrap and using stock Ford diff fluid I was getting axle overheats on hot days in less than 15 minutes of track time. By contrast Shannonville is a very wiggly track with much lower speeds and I never got diff overheats there, the average lap speed is around 75 mph or so. Higher speeds = higher heat. I get that a Torsen makes less heat than a clutch diff does, but it still makes heat and is subjected to heat generated from the car itself from several different sources.
I did endurance racing back in the 90s, drove another guy's Camaro with a clutch type diff, it was an ex-PlayersGM series car and they had many bespoke driveline pieces on them. You could not keep rear ends in those cars even in sprint racing. The only way to make those diffs live back in the day was to virtually lock them solid so there was zero clutch slip, or as close to zero as you could get. Even at that the diffs needed a rebuild every 10 hours. It was funny watching them drive around in the pits, the inside rear wheel would hop trying to keep up with the outside wheel. Those cars had a grand total of 220 hp, less than half what our cars have today, and they still ate rear ends.
Those cars were lucky to see 120mph up the back straight, this car sees 147 mph up that same back straight. They ran 1:41 laps, this car runs 1:33s. Higher speed = higher heat. Torsen or not, there's a limit to the heat they can stand, which is why Ford put a heat sensor in the rear end.
The stock exhaust runs very close to the diff so I wrapped the exhaust for 4 feet around the diff area and that along with Red Line fluid helped a lot. I haven't had a diff overheat for the last 2 years. But I also know what triggers it and I tend to avoid those conditions, which you can easily do when you're just lapping. I had a diff cooler spec'd out but decided it was not necessary, if the driver manages the problem correctly. I've learned how to do that and no longer get axle overheats. The car is heavy enough without adding more to the weight problem.