Today’s multi-speed transmissions have to contend with ever increasing operating temperature due to increased vehicle loads and towing capacities, coupled with inadequacies of OEM built-in cooling systems.
The resulting excess temperature is a common cause of premature transmission failure as the attached chart shows:
Did you Know???
For every 10 degrees F of heat reduced, you double the life of the transmission fluid. For every 20 degrees F of heat reduced, you double the life of the transmission!
1. Choosing a cooler – which is better?
When it comes to choosing between the various coolers in the market, cooler construction plays an important part in today’s modern installations. Factors in deciding which style of cooler to use include oil flow capacity; low-pressure drop; available size; minimum airflow disruption and hose end fitting type and size. A low-pressure drop plate and fin type cooler is 30% more efficient than a tube and fin type cooler because the cooling circuit operates at a regulated low pressure. Hydraulic engineering formulas equate that a 90-degree bend has the same restriction as 7.5m of straight pipe. Most tube type coolers have 180-degree bends (that is, 2 x 90-degree bends at the end of each run) and there are usually five of these bends in each cooler, so that is the equivalent of 75m of cooler line, resulting in increased pressure drop in a tube and fin type cooler. A much larger surface area is also required to achieve the same cooling capacity compared to a plate and fin type cooler.
More efficient “Plate and Fin” Cooler
Plate and Fin Coolers – The plate and fin cooler can be distinguished by the parallel plates that run horizontally, and looks just like a mini radiator. This type of transmission cooler is more efficient than the tube and fin type, mainly because the larger surface area allows for more fluid to contact the cooling surface. Fluid is forced through each row of smaller plates that help to cool the fluid faster and more effectively.
Tube and Fin Coolers – The tube and fin cooler can be distinguished by the tube that weaves throughout the transmission cooler and the turbulators that surround it. The tube is responsible for transferring the fluid around while the fins attached on the outside help to absorb the heat. Tube and fin coolers are often a less efficient type of cooler.
Less Efficient “Tube and Fin” Cooler
2. Does size matter?
When it comes to selecting the right size cooler for the vehicle, the rule of thumb is to select the largest size you can comfortably fit in the space available. I am yet to hear of any one over cooling their automatic transmission although a cooler that is too large may not allow the transmission to reach optimal operating temperatures. Correct hose sizing is also critical. Vehicle specific kits are becoming more popular, with most manufacturers offering either a GVM rating or a thermal unit rating to help with size selection if the unit is a custom fit up.
3. Fitting the cooler
When deciding if you should install the cooler in series, or to fully bypass the radiator, consider the following points. Will the vehicle be towing a light or a heavy load, will the vehicle be used for off-roading, or has the vehicle been performance modified? Fully bypassing a failed heat exchanger is often more cost effective and eliminates the potential for any future coolant and oil contamination. Consideration should also be given to the prevailing climate, with vehicles operating in hotter conditions leading to extra heat load being placed on the cooling system.
4. After installation
After installation, an important tip is to always remember to top up the transmission fluid after installing an oil cooler. Normally around one litre will suffice but be sure to follow the vehicle manufactures recommended fill procedure and to use the correct Automatic Transmission Fluid for the vehicle.
EXEDY has a full range of coolers available under the Coolmaster brand, including the newly launched Coolmaster Off Road range for popular 4X4 applications. Visit www.exedy.com.au and search for your vehicle on the Parts Finder for more information.
