6 Easy Ways To Combat Transmission Fluid Overheating

The automatic transmission is a sophisticated hydraulic coupler. That means the function it performs is aided by fluid. When that fluid gets overheated, the transmission will soon fail. Not maybe, it will. Heat generation is serious enough with a stock unit, but if you add performance-enhancing items like a stall converter or a transbrake, heat generation is exponentially increased. Since Chevy Hardcore is here to help enthusiasts, I thought it would be prudent to give you guys a few tips and show you some worthwhile upgrades from Speedway Motors that you can install on your ride to help combat the effects of heat.

According to Mike Long of DeWitts Radiator, “the longevity and performance of the transmission can be maintained by a keeping a constant temperature. Internal transmission coolers are submerged within the radiator and act as both a preheater and cooler to maintain desired and sustained temperatures. It’s no surprise that adding an external unit can offer a greater cooling ability because it’s not submerged in heated engine coolant. There are many variables to consider when selecting the proper external cooler. Sustained speeds, daily-driving patterns, and higher temperature climates may only require an internal cooler. Additional power-adders, competition driving, or track days may require an additional external cooler. These coolers can be placed inline to add additional area and fluid capacity to promote cooling.”

Pass The Cooler

tranny cooler

Since one of the easiest and least expensive upgrades you can install is an external transmission cooler, something to keep in mind is that coolers come in different styles and although they essentially do the same thing, they are different.

The main difference is in the ability of the cooler to actually lower the temperature of the fluid. The most economical is the tube-and-fin style. This cooler has a tube that weaves back-and-forth through the cooler. Aluminum fins attached to the outside of the tube help dissipate heat quickly. Although this is a more economical style of cooler, its efficiency is limited when compared to
other designs meant for transmission fluid.

“Unlike an engine radiator’s tube and fin design, transmission coolers require components rated for use at higher pressures,” states Mike. “These coolers are typically stuffed tubes with a turbulator placed into the tube. This creates a turbulent flow to aid cooling and creates internal trusses to hold the tube’s shape. They are also an extruded tube with formed channels or a stacked plate style with a placed internal turbulator. The common factor being the turbulator adding cooling function and strength.

 

tranny coolerNext up is the plate and fin cooler. While these basically work the same as the tube-and-fin-style cooler, they are more efficient. As the fluid is forced through the plates-and-fins, the smaller, flatter plates allow more fluid to contact the aluminum surface inside the cooler.

Turbo-What?

As fluid flows through the cooler, it develops a boundary layer. This boundary layer is described as the outer surface area of a fluid flowing through a tube or plate. This outer layer (surface area) of the fluid will “stick” to the wall of the tube or plate. As this fluid sticks to the cooler, cooling efficiency is decreased. This is because the fluid contacting the tube does not move as fast as the fluid encased within this boundary layer. To ensure all the fluid moves as needed, Turbulators are introduced into the cooler’s tube or plates. Adding turbulators will alter fluid flow by disrupting a smooth flow and create a turbulent flow. The turbulator creates a larger surface area to aid in heat dissipation while bonding the plate or tube cross-section together for added strength. It also optimizes the fluid flow and pressure within the cooler for the greatest efficiency.

transmission coolerAnother cooler style are stacked-plate coolers, which are the most efficient cooler design. These units are designed the same as the plate and fin style, but they include high-flow turbulators (fluid agitators) within the pates to help lower the fluid temperature. These are the best coolers for heavy-duty towing or race applications. Also, instead of a bulged-end tube that accepts a hose and clamp, this cooler also uses AN fittings for cooler-line connections.

 

Transmission coolerRelatively new on the market are heat-sink coolers. These are not the most well-known type of transmission cooler but are still used. These coolers utilize a unique finned aluminum design that disperses heat throughout the body of the cooler without the use of incoming air, unlike other transmission coolers. Since they do not need air flowing through them, they can be mounted almost anywhere. Because of their design, heat sink coolers can be mounted almost anywhere.  However, the mounting location chosen can make it hard for the cooler to be as effective as other types of transmission coolers depending on how much airflow it encounters to aid with heat dispersion.

Finally, Mike has this to add, “Cooler placement is crucial. Stacking the cooler in front of another heat exchanger, condenser, or radiator may cause an unwanted pressure drop across the stack, minimizing the efficiency and cooling performance of other key parts of the cooling system. A high-performance fan or added fan may be needed. Determine the area of the vehicle  where the cooler will be mounted and how airflow is fed to that area.”

Fluid Temperature And Damage

  • 220 degrees – varnish forms on metal surfaces
  • 240 degrees – seals begin to harden
  • 260 degrees – transmission bands and clutches begin to slip
  • 295 degrees – seals and clutches burn. It’s time to call a tow truck

Pan Handled

While a chrome pan might look cool, the chrome really doesn’t add any benefit other than its good looks. If you’re looking for an upgrade that adds good looks and helps the transmission, try a deep pan. These are available in either stamped steel (in shiny chrome) or cast aluminum. While a stock Turbo 350 transmission pan will hold roughly four quarts of fluid, a deep pan will typically double that capacity. How does that help, you ask? A deep transmission pan allows the transmission to hold an extra three to four quarts of fluid. The added capacity affords the fluid the ability to cool down more thoroughly before being circulated back through the transmission. Combine a deep pan with an external transmission cooler, and you have done your transmission a great service.

If having a deeper-than-stock transmission pan is a good thing, adding a way to cool the pan has to be a great idea, right? We found this deep pan with cooling tubes that just might be the best way to cool your fluid even more than with just an external cooler. Within the pan are brazed, turbulator-equipped airway tubes passing through the lower section of the pan for more efficient cooling. If the added fluid aids in cooling, just imagine how much the air passing through the tubes can enhance that help.

While parts that increase a hot rod’s engine and suspension performance seem to get all the glory, hopefully, we have offered you guys some information that can help your classic deliver years of reliable service to go with that added performance. When your ride doesn’t break, that leaves more money for even more performance parts, and that’s a great thing.

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About the author

Randy Bolig

Randy Bolig has been working on cars and has been involved in the hobby ever since he bought his first car when he was only 14 years old. His passion for performance got him noticed by many locals, and he began helping them modify their vehicles.
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