An external trans cooler is...
An external trans cooler is cheap insurance for your automatic during particularly stressful motoring excursions. Like the advertisements say, heat is your transmission's worst enemy; B&M advises that typical operating temps for an automatic trans remain between 150-200 degrees F, with an ideal temp around 175. Since engine coolant temps are often higher than this, particularly on late-model vehicles, the small OE trans cooler in the radiator is barely adequate for high-performance or heavy-duty use. The B&M Supercooler is a complete kit that includes plumbing and mounting hardware in addition to the plate-type cooler.
No matter what part of the country you find yourself in, summer is prime time for cruising, racing, or whatever you like to do with your "fun" cars. Of course, it's also the time for intense temps and lots of traffic. So, whether you're out on the racetrack or sitting in traffic trying to get there, your drivetrain is likely being subjected to its worst enemy: heat. We were made acutely aware of this during last summer's Hotchkis' Track Day. First, the tow vehicle (former Caltrans laborer, Project Jake) was brutalized over California's infamous "Grapevine": a stretch of the I-5 that traverses grades serious enough to concern even the most calloused truckers. Then there was the event itself, featuring long open-track sessions on Buttonwillow's rather fast road course--lots of fun, but also a serious workout for any vehicle when overly competitive motoring journalists are driving.
The instructions advise installers...
The instructions advise installers to plot cooler placement prior to beginning the installation to affirm that the unit can be mounted properly and that the fluid lines can be routed as directly as possible. This early Camaro has plenty of room up front to mount the cooler in front of the radiator. B&M considers this the ideal location, and classifies the cooler as having 100 percent of its potential efficiency like this. If there were an A/C condenser in front of trans cooler, efficiency would drop to 75 percent, and mounting the cooler on the engine side of the radiator drops efficiency to 60 percent.
Vehicles intended for this sort of use are generally built with extra cooling capacity, and many have gauges, or at least warning lights, to keep drivers apprised if any of the vital fluids exceed safe temps, except of course, the automatic transmission fluid. This nearly universal oversight may be because trans temps are not a major concern on typical road-going vehicles, but all it takes are a few hot laps at a racetrack or an extended Second-gear hill pull with a loaded trailer to saturate the entire fluid capacity of the average automatic with heat. What follows is often disastrous and expensive.
So, after being reminded of these facts, we were motivated to upgrade the fluid cooling abilities of a few of our fleet. An external transmission cooler is a time-tested method of enhancing the transmission's cooling capacity and is relatively simple as well. Similarly simple is the practice of increasing total fluid capacity with a deeper pan. We went to one of the original sources of automatic transmission performance, B&M, and ordered a universal Supercooler kit and a cast-aluminum deep pan kit in the hopes that our automatics will be better equipped to survive the next heavy-foot episode.
 Often, external trans coolers...  Often, external trans coolers are plumbed so that they replace the stock in-tank radiator cooler, but most OE and trans cooler manufacturers recommend retaining the factory cooler, using the external cooler to increase the system's heat-transferring capacity. Proper routing passes the fluid through the radiator cooler first, then on to the external cooler before heading back into the transmission. |  Here's another common mistake:...  Here's another common mistake: cutting the steel hardlines for the factory cooler and sliding standard rubber fuel hose over it with hose clamps. Even with multiple clamps, this is bound to fail eventually as the pressure in these lines can reach the high side of 200 psi during extreme use (such as high-rpm racing). Once the fluid seeps under the clamped portion, the hose becomes lubed and slips off. |  B&M provides brass fittings...  B&M provides brass fittings that thread onto the fittings on the factory cooler lines, providing a series of barbs to secure the hose connection. Similar male-ended fittings are provided to thread into the radiator. |