We all have transmissions in our trucks, like it or lump it, and we'd bet that automatic transmissions are under the floorboards of most of the classic trucks on the road today. Many have eliminated the third pedal and added a modern automatic, whether it be a three-speed or an overdrive. And yet with that said, very few of us know how they work, and most don't care as long as they are working. But what do we need to keep our automatic transmission doing just that?
Of the many scenarios that could go wrong with an automatic transmission, it is unanimous among those in the transmission industry that heat is the number one killer. A properly maintained transmission (i.e. fluids changed regularly and properly cooled) should last anyone a good amount of time and miles, but as soon as that fluid temp goes up, you can start counting down to its demise.
Don't Lose Your Cool
What kind of operating temps should you expect from your automatic? According to TCI, the ideal operating temperature for automatic transmission fluid is between 175 and 225 degrees. At approximately 240 degrees, important additives in automatic transmission fluid (ATF) begin to cook. The result is the formation of varnish inside the transmission. At approximately 260 degrees, internal transmission seals (which are typically manufactured from a polyacrylate material) begin to harden. The end results are leaks, both internal and external, simply because the seals lose their elasticity. At approximately 295 degrees, transmission clutch plates begin to slip because the oil is breaking down further; at roughly 315 degrees, seals and clutches effectively burn out. When carbon forms in the oil, for all intents and purposes, the transmission is junk. A typical transmission will die within 2,000 miles if subjected to 300-plus degree heat.
There are many ways out there to cool your transmission fluid down, from a stock in-radiator unit, an external tube-and-fin design, a stacked-plate type, and the long-finned cylinder style, to name the most common. Obviously, something is better than nothing, but placement has a lot to do with the efficiency of an external tranny cooler. The more air you can get into the cooler, the better it will cool, just like with a coolant radiator. Since most tranny coolers are fairly small, the best place for them is in front of the radiator. This is easily done with most coolers since they are usually fairly small and come with the necessary hardware to do so.
Greg Ducato of Phoenix Transmission Products spoke very highly of the stacked-plate-style coolers like B&M's SuperCooler that are made from 100 percent aluminum and use stamped plates sandwiched together to create one of the most efficient oil cooling devices available. Not only does this unique design provide for maximized cooling through more efficient heat dissipation, but it also provides a much sturdier cooler that is very resistant to flying rocks, bugs, and other debris.
According to TCI, its Max-Cool tranny coolers, also a stacked-plate design, cool 33 percent better than tube-and-fin coolers. If you have a little extra money, it sounds like upgrading to a stacked-plate tranny cooler would be a wise idea. Stacked-plate-style coolers seem to be the smallest, most efficient, strongest, reasonably priced transmission coolers out there today.
This is not to say that a tube-and-fin-style cooler shouldn't be used. They still do the job, which is better than nothing, and have worked well over the years to cool many a transmission, but just double check with your transmission/cooler's manufacturer to get the right GVW rating for your application.