Is a transmission cooler the way to go, if you want a little extra transmission insurance?

Dear Car Talk

Dear Car Talk | Aug 01, 2008

Dear Tom and Ray:

I have a disagreement with my son. Well, actually I have many, but one in particular goes like this: He says an add-on transmission cooler (small radiator) will enhance the performance and life of the transmission. I say it doesn't help unless you have high-stress demands, like a lot of towing. Who wins this one? -- George

TOM: I think your kid's just looking for something to do, George. And if you don't let him put a transmission cooler on your car, he's going to build an intercontinental ballistic missile in the basement.

RAY: I'm afraid the kid's theory is correct, though. While it won't enhance the car's performance, a separate cooler will lengthen the life of the transmission.

TOM: The transmission should last the life of the car without an auxiliary cooler. Of course, it doesn't always work out that way, as the people at AAMCO can happily tell you.

RAY: While there are many ways a transmission can fail, overheating fluid certainly is a leading cause. When the fluid overheats, it breaks down. And then it stops lubricating properly, which is what ultimately harms the transmission.

TOM: To give you an idea of how hot transmission fluid gets, even under normal conditions, almost every car runs the transmission fluid through the radiator coolant to cool it off. The radiator coolant is 200+ degrees. That's being used to COOL the transmission fluid!

RAY: So, if you want to buy some extra insurance for your transmission, a transmission cooler is the way to go.

TOM: Does everybody need one? No. Most people don't keep their cars forever. And even those who do often find that something else leads to the car's demise before the tranny goes -- like bad rings, or a run-in with a bread truck. So we're not saying everyone should go out and buy a transmission cooler.

RAY: The people who should get one are those who tend to put the greatest stress on their transmissions. And as you correctly say, George, that comes from activities like towing things, driving in the mountains or loading up the car with a couple of mothers-in-law.

TOM: But your kid is right. In general, a transmission that runs cooler will last longer.

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