Transmission Cooler Essentials

[Airstreamer67]

Many manufacturers use idiot gauges because consumers too often do not know what the values mean, take advice from others with the same problem, and drive the dealers nuts trying to placate them.

I've seen a popular "tranny temp" chart on the Internet which shows a tranny will die in about 20 miles at the temps cited above. Of course, that chart is old and without documentation. But it's still widely cited as fact.

[dznf0g]

I had a similar chart waaaayyy back when I was in school. The 20 minute failure was at above 300* as I recall. However, there have been 6 generations of trans fluid since then. For example Dexron VI for GM and similar for Mercron and Mopar. With today's fluids, I wouldn't even install an additional external cooler unless I saw consistent and regular temps above 220*. A once in a while spike while towing, is nothing to worry about. And the "idiot" gauges have nothing to do with anything anymore. All the modern vehicles will intervene and prevent sudden temp spikes with trans shifts and high speed fan activation, and if you ignore things, they go into limp mode to protect themselves.

That being said, you won't hurt anything with an additional cooler, unless you live in the far, far north (arctic). Overcooling (for the vast majority of us) is as much a myth as is "250* is too hot and damage is being done". Modern trans fluids are quite remarkable.