My gearbox is 35 years old. To give it a chance to hold another 35 I replaced the default anemic cooler with this one. I have a temp sensor before and after the cooler to see how much cooling it provides. On a chilly morning, while towing a small trailer down a slight incline, I saw it cool down to 30 degrees without the fan running. (fan doesn't come on until 185) Cheap insurance and even if the transmission fails it can still go on my next truck.