mcgarvey
Veteran CEG'er
Hopefully the mods decide to make this a sticky. It seems to be a frequently asked, though poorly addressed, question.
Fittingless Hayden #404 Transmission Cooler Installation
It’s been claimed that installation of a tube-and-fin type transmission cooler will effectively double the life of your CD4E transmission, which we all know is prone to a severe overheating condition that can cause premature failure.
There are plenty of threads and how-tos on how to install this, but they all vaguely refer to pipe fittings that are necessary without giving part numbers for them. The way I am about to describe, there is no need for fittings.
Buy a Hayden #404 Transmission Cooler. It will come with the cooler itself, a few feet of rubber hose, and four hose clamps. Also, beg, borrow, or steal a pipe flaring tool. Before you start, see the attached image. The graphic I made is only intended as a schematic for hooking up the fluid connections, so follow these directions carefully.
1. Cut the piece of hose in half. Using the supplied clamps, attach a piece to each outlet of the cooler.
2. Mount the cooler. It is best to mount it all the way to the front, ahead of the power steering cooler, which is just a loop of hard tubing forward of the radiator. Use zipties and foam padding to carefully, but securely fasten it in a location where it will get maximum airflow. Ensure that the hose outlets point toward the passenger side.
3. Now, for the fun (read- messy) part. Look for the crossmember that the radiator supports attach to. Running along the front of it are two hard steel lines. These are the lines to the stock transmission cooler. Both lines go back to the tranny case at one end. At the other end, one attaches to the top of the radiator, and the other at the bottom. We’ll be working with the bottom line, because this is the fluid return. As near as you can to the far right end of that line, use a pipecutter to cleanly cut the line. A good amount of fluid will come out, somewhere around a quart immediately. It will continue to drip as long as it’s open. Cut the line again further to the left side of the car by a few inches. There should be a gap of maybe 6-7 inches.
4. Use the flaring tool to flare both ends of the hard cooler line. This is accomplished by selecting the right tubing size on the tool (3/8”) and then twisting the flare cone down. You will be left with two flared ends into which you can splice your auxiliary cooler.
5. Route your new cooler hoses that you’ll be attaching. I recommend running them alongside the power steering hoses, above the right-hand radiator support and then to the cut in the hard line. Place the hose clamps on the pieces of flexible hose and slip the hose ends onto the flared ends of the hard stock cooler lines. It does not matter which one goes where. Tighten the hose clamps securely.
6. Secure the connections with zipties or some kind of bracket. This is very important. A flare/clamp connection makes a good seal unless it is moving. If you do not immobilize the connection, you will definitely have a fluid leak.
7. Add about a quart of Mercon to the transmission to make up for the fluid lost and the increased capacity.
8. Start the engine and look for leaks. Adjust fluid level with dipstick as necessary. Retighten hose clamps after a few days, and keep looking for leaks.
9. Discard the fitting that came with the cooler, as it is completely useless. Enjoy the smoother shifting and worry less about your CD4E taking a dump on you when you least expect it.
Fittingless Hayden #404 Transmission Cooler Installation

It’s been claimed that installation of a tube-and-fin type transmission cooler will effectively double the life of your CD4E transmission, which we all know is prone to a severe overheating condition that can cause premature failure.
There are plenty of threads and how-tos on how to install this, but they all vaguely refer to pipe fittings that are necessary without giving part numbers for them. The way I am about to describe, there is no need for fittings.
Buy a Hayden #404 Transmission Cooler. It will come with the cooler itself, a few feet of rubber hose, and four hose clamps. Also, beg, borrow, or steal a pipe flaring tool. Before you start, see the attached image. The graphic I made is only intended as a schematic for hooking up the fluid connections, so follow these directions carefully.
1. Cut the piece of hose in half. Using the supplied clamps, attach a piece to each outlet of the cooler.
2. Mount the cooler. It is best to mount it all the way to the front, ahead of the power steering cooler, which is just a loop of hard tubing forward of the radiator. Use zipties and foam padding to carefully, but securely fasten it in a location where it will get maximum airflow. Ensure that the hose outlets point toward the passenger side.
3. Now, for the fun (read- messy) part. Look for the crossmember that the radiator supports attach to. Running along the front of it are two hard steel lines. These are the lines to the stock transmission cooler. Both lines go back to the tranny case at one end. At the other end, one attaches to the top of the radiator, and the other at the bottom. We’ll be working with the bottom line, because this is the fluid return. As near as you can to the far right end of that line, use a pipecutter to cleanly cut the line. A good amount of fluid will come out, somewhere around a quart immediately. It will continue to drip as long as it’s open. Cut the line again further to the left side of the car by a few inches. There should be a gap of maybe 6-7 inches.
4. Use the flaring tool to flare both ends of the hard cooler line. This is accomplished by selecting the right tubing size on the tool (3/8”) and then twisting the flare cone down. You will be left with two flared ends into which you can splice your auxiliary cooler.
5. Route your new cooler hoses that you’ll be attaching. I recommend running them alongside the power steering hoses, above the right-hand radiator support and then to the cut in the hard line. Place the hose clamps on the pieces of flexible hose and slip the hose ends onto the flared ends of the hard stock cooler lines. It does not matter which one goes where. Tighten the hose clamps securely.
6. Secure the connections with zipties or some kind of bracket. This is very important. A flare/clamp connection makes a good seal unless it is moving. If you do not immobilize the connection, you will definitely have a fluid leak.
7. Add about a quart of Mercon to the transmission to make up for the fluid lost and the increased capacity.
8. Start the engine and look for leaks. Adjust fluid level with dipstick as necessary. Retighten hose clamps after a few days, and keep looking for leaks.
9. Discard the fitting that came with the cooler, as it is completely useless. Enjoy the smoother shifting and worry less about your CD4E taking a dump on you when you least expect it.
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