by VANagain Mon Aug 10, 2009 12:40 pm
My radiator has the tranny cooler built in because it came with a PowerGlide. But since we are always trying to keep our engines from overheating, common sense would tell us NOT to run the tranny fluid thru it. However, the instructions from Bowtie Overdrive where I bought my rebuilt 700R4 say to run the lines thru the radiator even if you do have an auxiliary cooler. AND they say to run it to the radiator FIRST, which I'm hesitant to do. Why not AFTER it's had a chance to get cooled thru the auxiliary cooler first?
Here are some excerpts from their lengthy instructions. They are for a 700R4 but should be applicable for any automatic tranny:
Always run the transmission fluid through a transmission heat exchanger built into your radiator. Most installations don’t even require additional coolers if the radiator system is well designed. When you plan to tow, you should try to over kill this requirement. If you must error while designing a cooling system for your transmission, please do so on the safe side of the equation, on the side of supplying a little more cooling than is needed, rather than not quite enough.
The number one cause of failure with these transmissions is continuously running the transmission fluid hotter than it is designed to tolerate or frying the fluid during a single catastrophic incident. Considering the cost of a high performance motors and these automatic overdrives, we have never been able to understand why the Hot Rod community in general has such a cavalier attitude about the cooling requirements of these two costly items. We have had professional custom car builders tell us they don’t have room for a cooler in the radiator! We’ve had them tell us their customers don’t want ugly hard lines going to the radiator. Just because you don’t have room for a heat exchanger in the radiator or don’t like the looks of the cooling lines won’t stop their fluid from burning up!
Use the largest flat tube cross-flow style cooler you can afford. Install this cooler in front of the car’s radiator. Force air to be drawn through this cooler by mounting it as close to the radiator as you possibly can. These types of coolers are only effective when air is actively flowing across the fins and tubes. Make sure your cars cooling system has a fan shroud and the fan is positioned correctly in relationship to the shroud. The size and quality of the cooler is meaningless if air is not forced to remove the heat by flowing over the fins and tubes! If you live in a very cold winter location you will need to install a proper bypass system to control the direction of fluid flow through this cooler in the wintertime. You can avoid over cooling the fluid this way. These bypass systems avoid over cooling by changing which cooling device the fluid flows through last. In the summer time you want all the cooling you can get, so you want the auxiliary cooler last in the system. In cold winter climates you want the radiator water to maintain proper transmission fluid temperature so the fluid needs to flow through the radiator cooler last. Some areas get very cold and stay that way through the entire winter. In these areas you should completely bypass the auxiliary cooler from the system during the winter season.
Stop the vehicle and open the hood. Feel the return line from your cooling system. When you touch the return line, do so with caution, use a quick, light tap to determine if the line is scolding hot. You should be able to touch this line without burning your hands. Even the outgoing line shouldn’t be hot enough to burn you if you touch it momentarily. If you feel very high temperatures on the return line you should add a cooler. A transmission temperature gauge will help determine what is occurring. If you error on this topic, please do with too much cooling. The temperature gauge is recommended even if you don’t plan to tow. 150 degrees F or less should be indicated with a temperature probe (sender) positioned in the pan. The fluid can be seriously overheated if pan temperatures exceed 150 degrees F. This happens because overheating is occurring in the converter, not the pan.
