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A Good Transmission Oil Cooler Is A Worthwhile Addition
There was a time when most hot rods had only stick shift transmissions. We can remember running a ’39 Ford transmission behind several different engine combinations, which quite often ended up with gear teeth on the bottom of the transmission case. If the transmission didn’t break the rear axle in the ’40 Ford, the rearend would. It wasn’t a solution, but it was a start.
By the ’60s, rodders started improving their cars with more modern, open rearends and late-model four-speed transmissions. Today the vast majority of street rods run automatic transmissions, including many with automatic overdrive. If you are building a street rod with an automatic transmission, you will need a shifter to operate it and a transmission cooler to keep the transmission fluid temperatures at a safe operating level.
There are two different approaches to transmission coolers and, in the case of street rods, one works dramatically better than the other. One way is to order a radiator with a built-in transmission cooler, much as the auto manufacturers have done for years, and for customary street operation in a stock vehicle this works fine. For a street rod, however, the radiator size is generally smaller than that used in a modern production car, which limits its cooling capacity, both for the engine and the transmission. In this case it is better to run a separate transmission cooler capable of transferring enough heat without adding to the task of transferring heat from the engine. The separate transmission oil cooler leaves the radiator with only the job of cooling the engine and keeping it at a safe operating temperature. That is even more important if your car is equipped with air conditioning, as the incoming airflow has to go through the condenser before it enters the radiator.
There are a variety of good transmission coolers available; however, for this application we will use a Flex-A-Lite model. This cooler is easy to install and fits inside the ’34 Ford framerails, and the price is reasonable. If you are going to run a small transmission, such as a Turbo 350 or a Ford C4, the cooler size can be smaller than one for a Turbo 400, C6 or an overdrive transmission, but remember that when it comes to cooling, overkill isn’t a bad thing. This cooler is designed to work great in these applications, and it will fit under a wide variety of street rod chassis. We followed the installation and found that it can be done using normal hand tools and your choice of a 3-inch cutoff wheel or a large chop saw.
