Frequently Asked Questions About Transmission Coolers

Best Transmission Coolers

transmission cooler placement diagram

Because your automatic transimssion works harder when you tow, it can get hotter, and heat is one of the major enemies of your transmission. An aftermarket transmission cooler can keep your transmission from getting too hot, helping you get the best performance and long life out of it.

If you are considering a transmission cooler, you may have questions. If so, we have some answers. Check out the questions, below, to find out more about transmission coolers.

1. How does a cooler function?

Fluid heated by the transmission, engine, or power steering pump flows to the cooler. The air moving over the fins of the cooler cools the fluid, which is then routed back to the transmission, engine or power steering pump in a continuous loop through the return line.

2. How do you attach the transmission cooler in front of the radiator or air conditioning condensor?

Several different options for mounting a transmission cooler are available. In the most common installation method, the cooler is attached with narrow plastic rods, pads, and fasteners. The plastic rods are run through the transmission cooler and the radiator or air conditioning condensor and secured with the fastener. Another option is to use a rigid mount kit that includes bendable brackets to mount the cooler. You can use this option if the cooler has mounting points designed for brackets and your vehicle has suitable mounting points. A third option that consists of solid mounting brackets is available for stacked-plate type coolers.

Click here to see available mounting kits for transmission and engine coolers

Tube and Fine Cooler

3. What is the difference between the tube-and-fin cooler, the plate-and-fin cooler and the stacked-plate cooler?

The main difference is in the ability to cool the fluid. The tube-and-fin style has a tube that carries the transmission fluid through the cooler. It is also distinguished by its turbulators, which agitate the fluid to get more of it to contact the aluminum in the tube. Aluminum fins are attached to the outside of the tube and, since aluminum dissipates heat quickly, the heat from the fluid is absorbed by the aluminum, moves out to the fins, and is then carried away from the cooler by the air flowing through the fins on the outside of the cooler. This style of cooler works well but is the least efficient type of cooler that we carry.

Plate and fin cooler

Plate-and-fin coolers work on the same principle as the tube-and-fin-style coolers but are more efficient. Plate-and-fin coolers force fluid through much smaller plates that, like the tube-and-fin cooler, cause turbulation (or agitation) of the fluid. But fluid in the plate-and-fin style is cooled better before leaving the cooler because the smaller, flatter plates allow more fluid to contact the aluminum surface inside the cooler.

Stacked plate cooler

Stacked-plate coolers are the most efficient coolers. They have the same design as the plate-and-fin style, but they have high-flow turbulators for heavy-duty towing or race applications. The stacked-plate design uses AN (Army-Navy) fittings, which are popular in high-performance and racing applications where the cooler may need to be installed and removed more frequently than in a typical towing setup.

Best cooler location

4. If there are 3 coolers all listed for the same weight, how do you know which one is best?

The first consideration would be the size of the cooler. Generally speaking, the larger the cooler, the better the cooling performance will be. If there are similarly sized tube-and-fin coolers and plate-and-fin coolers, then the plate-and-fin cooler will perform better even if it is slightly smaller. The second consideration is the mounting location. If you mount the transmission cooler behind the radiator or between the radiator and air conditioning condenser, a more efficient cooler is required to provide the most efficient cooling.

5. Why are coolers rated by Class?

Because we are in the towing industry, our customers are used to seeing Class ratings on their trailer hitches, so this is an easy way to alert the customer as to which cooler is the most efficient for their towing needs. Therefore we use the Class rating to let customers know that if they have a Class II hitch on their vehicle, then a Class II cooler should be sufficient, but they can always use a larger cooler for more cooling if they like.

6. Shouldn't I get the one rated for the highest weight capacity? Why or why not?

The general rule is that transmission fluid cannot be cooled too much, so using the largest cooler that will fit is a good idea, especially if you are towing. The only reason not to add the largest cooler possible would be if you live in a very cold climate where temperatures are commonly below 0 degrees and you have a transmission cooler installed. This would warrant warming the engine for a few minutes. Most people warm the engine in these cold conditions anyway, so size is not a factor.

7. Will this mess up my factory transmission?

No. As long as it is properly installed, a transmission cooler will not affect a factory transmission. It is a flow-through device and does not affect any internal components of the transmission. A transmission cooler will just help to prolong the life of the transmission by keeping the fluid cooler. Transmission fluid cannot be cooled too much, so the addition of a cooler is a good idea, especially if you are towing.

8. Does the transmission cooler do anything if you are not towing?

Yes. The transmission cooler is a flow-through device and operates anytime the engine is running. The fluid will flow from the transmission to the OEM cooler and then to the aftermarket cooler; and finally, the cooled fluid flows back to the transmission in a continuous loop.

Custom fittings

9. If the transmission cooler is a custom fit why do I need to measure?

The cooler itself is not the custom-fit part. We have transmission coolers in the fitguide because some vehicles, mostly GM, Ford and Chrysler/Dodge, can use custom fittings to make installation of the transmission cooler easier and faster.

10. Are custom fittings available for most vehicles?

No. For most vehicles you will use an Insta-dapt fitting that is included with the transmission cooler and that connects directly to the OEM transmission cooler. Then the rubber hose going to the aftermarket transmission cooler is clamped to the fitting, and the hose coming from it is slipped over the original line and clamped. Or, the Insta-dapt is installed in-line between an OEM hose and the transmission cooler hose.

In addition, some vehicles will require that you cut and flare the OEM steel or aluminum transmission return line and then clamp the transmission cooler hoses directly to the two ends of the cut line. Note: Many installers prefer this type of installation because they already have the cutting and flaring tools and no extra fittings are needed.

11. How do I install a transmission cooler when special fittings are available?

Special fittings are designed to make it easier and faster to install a transmission cooler. Most vehicles for which fittings are available have either snap-in fittings or threaded flare fittings that can be used to connect the rubber hoses going to and coming from the aftermarket transmission cooler in-line with the transmission's return line and the OEM transmission cooler.

12. How do you know if you need special fittings?

Our year-make-model fitguide will list the special fittings needed for a specific vehicle if they are available from our supplier. This is why transmission coolers are listed in the fitguide on our website.

hose barb fitting

13. What is a hose barb?

A hose barb is the part of a fitting that the rubber hose slides over. The hose is then secured with a hose clamp. Often the transmission cooler will have hose barb fittings for connecting the rubber hoses to it.

Click here to shop for radiator adapters.

14. What does NPT mean?

NPT fittingAN fitting

NPT stands for National Pipe Thread, which is a standard for threaded fittings in the plumbing industry. Much like AN (Army-Navy) fitting, it is a way of identifying the type and size of fittings needed for an installation application.

15. Can all coolers be used on any vehicle out there or are the ones listed in the fit guide search only for that year, make and model?

A transmission cooler is a flow-through device and is not designed specifically for any particular year, make and model. Any cooler can be used on any vehicle with an automatic transmission, provided that it will fit in the location where the customer wants to install it. Year-make-model fittings are available for some vehicles to make it easier to install the coolers. You can use the fitguide to determine whether a vehicle can use a custom fitting.

16. Just because the fitguide does not list a transmission cooler for a vehicle can someone still put one on?

Yes. The installer will need to determine how to install the cooler on the vehicle. Any of the installation procedures explained previously can be used. We do not list a transmission cooler if we do not have information from the transmission cooler manufacturer or when the vehicle manufacturer does not recommend installing a transmission cooler on the vehicle.

combination cooler

17. Can I use an oil cooler, power steering cooler and transmission cooler all together?

Yes. You can install all three on the vehicle. You would need three separate coolers and have the space needed to install each one. We carry some dual-function coolers. These are basically two separate coolers in one with an inlet and outlet for two different fluids.

Click here to see available dual-function coolers.

18. Do the coolers mount in the same location as other items, like power steering coolers and engine oil coolers?

Best cooler location

Yes. If you are installing more than one cooler you will need to carefully consider the fit. As long as there is enough room, it is possible to install all three coolers.

19. I have lines running from my transmission to my radiator. How does the transmission cooler actually install to the radiator?

Transmission coolers do not attach to the radiator. They attach in-line with the transmission fluid return line. It is common for an OEM transmission cooler to be built into the radiator tank to be cooled by the coolant in the radiator.

20. Does the transmission cooler need to be installed with the hose fitting in any certain position?

No. The cooler can be installed with the hose fittings in any position that will make the installation easier or look more professional on the vehicle. It does not matter which fitting on the cooler is used for the inlet or outlet.

21. Do I need an oil cooler also?

Oil coolers are optional. Many people choose an oil cooler when their towing application is heavy duty, such as towing a fifth-wheel trailer or gooseneck trailer. The oil cooler is based on the same flow-through principle as the transmission cooler. It is installed in-line with the vehicle's oil delivery system, and then the oil pump pushes oil through the cooler and back into the engine. If a vehicle manufacturer recommends an oil cooler for towing, then it would be needed for that vehicle. The customer should check the vehicle owner's manual.

Updated by: Raymond P.

Last updated: 7/3/18

Questions and Comments about this Article


Can I add ATF to the trans cooler lines that connect to the radiator? I replaced radiator on a 2009 Cadillac cts and had lost ATF when taking lines off. 102445

Reply from Jon G.

Does your radiator not have a cap to pour the fluid into? 75402


I have 4D56pajero diesel automatic .And my qns is can I drive the car only with transmission cooler without by passing to the radiator 98870

Reply from Jon G.

I'm honestly not quite sure what you're asking. If you're wanting to install a transmission cooler in a different way than it was intended then I would have to advise against it. 73579

Mike J.

Dodge 2019 Caravan: I just installed the Derale 13503 cooler. now i have an engine light. Do i need to top off the transmission fluid? 97816

Reply from Jon G.

Yes. Adding a supplemental transmission cooler increases the capacity of your transmission cooler system so you will need to add come coolant. 72908

Reply from David C.

@JonG you mean add some transmission fluid ! 73458

Reply from Jon G.

@DavidC Yes, that's what I meant. 73578

Rc S.

I live where is gets cold in the winter. That being said I understand that installing a trans cooler would be beneficial in the summer but would it hurt the transmission in the winter? Will the temperature of the fluid be detrimental to the transmission if it is too cold? 97617

Reply from Jon G.

As long as you let your engine warm up prior to driving around when it's super cold out (like you should already be doing) then you're going to have a difficult time getting that fluid too cold. 72909

Reply from Rc S.

@JonG yes we always warm the vehicle before driving in the winter. Thank you for the info. 72911

Pedro E.

My question is , when installing an aux trans cooler on a Tacoma 09 prerunner. would it be suggested to fill the radiator with transmission fluid ? 96219

Reply from Jon G.

It's my understanding that transmission fluid should only be put into the transmission cooler. 71051


I have a GMC Yukon XL Denali with a 6.2L engine. I saw your video installing the Flex-A-Lite transmission cooler FLX4118GMT, however I cannot find the same cooler with mounting bracket/hardware. Is it still possible to get the mounting bracket and hardware? Thanks! 95164

Reply from Chris R.

The Flex-a-lite Transmission Cooler # FLX400130 replaced that particular unit in the manufacturer's line. 70252

Ernest K.

I have a 1990 Buick Riviera. I am having a hard time finding the connecting lines from the transmission to the radiator. My lines are leaking & are rusted. Can you help me with a salvage yard or after market connectors for this problem? 86290

Reply from Chris R.

A transmission cooler will connect to the return line. An easy way to find this line is to simply shift the transmission into drive for about 15 seconds and then shut it off. Feel the lines to find the cooler of the two, which will be the return line. As for repairing the existing lines on your Buick my best advice it so simply visit a local auto parts store or mechanic - they should be able to help with this. 68242

Jared B.

I have a 2019 GMC Acadia SLT-1 but I do not see any transmission coolers for model years newer than a 2016 Acadia. Is there a specific part that I should be looking for or just go with the 2016 model year and the best rated for the space available? 84640

Reply from Chris R.

There's no particular reason a transmission cooler couldn't be installed on your 2019 Acadia nor are there any special parts/adapters that would be needed to do so. I'm honestly not sure why we don't have them listed. For your Acadia the Derale # D13503 should work really well. 67797


Any side effect of installing an atf cooler? It is physically blocking the air conditioning cooling which is designed to get air flow through the grill? 82016

Reply from Chris R.

There's really no harm with installing a transmission cooler. The unit should not block air flow to the point of causing any issues. 67388

Ruben G.

Could I refer to the video install of the Derale D15902 on the 2012 Toyota 4Runner for a 2010 4Runner? It should be the same...? 79091

Reply from Chris R.

Absolutely. The install process for the Derale # D15902 on your 2010 4Runner should be extremely similar, if not identical, to what's shown on the video for the 2012 model. I've linked the video below as well. 64098

Greg B.

Out of the 20 questions pertaining to transmission coolers not one gives any reason not to install one. A large number of transmission problems are attributed to heat, you do not need to use your vehicle to to tow or race to benefit from installing a trans cooler. 77724

Shane B.

Does mounting an auxiliary cooler up high top of the condenser cause more strain on the trans pump since its pushing the fluid up, lessening the life of the trans? 70996

Reply from Chris R.

Trans coolers are really designed to mount anywhere, so having it higher up above the condenser core wouldn't cause additional stress on the transmission pump to the point of shortening its lifespan. This would be perfectly fine to do. 57976

Rodney B.

Got a question I have an oil cooler on mine but Im not towing my camper yet how do I plug the lines 64861

Reply from Jacob H.

Having a transmission cooler installed when you are not pulling a trailer is not a bad thing. All it is going to do is provide extra cooling for your transmission. You can use a thermostat bypass # D13011 if you are not wanting the fluid to be running through the cooler all the time. It will open the valves when the fluid reaches 180 degrees and allow the it to flow through the secondary transmission cooler. 3/8" tubing bypass # D13011 1/2" tubing bypass # D15719 Mounting bracket # D25793 55023



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