This page will give you step by step instructions on how to install a transmission oil cooler for your 4th gen 4L60E (although the instructions will be pretty much universal to most auto transmissions I'm sure).

This is actually a very easy procedure as you'll see so don't think you need tons of mechanical experience to install one of these coolers :)

These are the basic parts that came in my transmission oil cooler kit.  This cooler is made to actually mount right on the front of the existing radiator and this kit comes with some fancy little zip straps that make mounting it a breeze!  In case you're wondering, I saw no increase in engine water temperature due to this tranny cooler covering up much of the radiator.

Here is the layout of the lines as they exist in your car.  Notice how the line coming from the tranny to the factory cooler has its rubber hose crimped to the metal tube and the return line going back to the tranny has a clamp?  This makes this job VERY easy... almost as if this car was designed to have an aftermarket tranny cooler installed right from the get go... hmmm :)  This brings up an interesting point.  I have heard of some bypassing completely the factory transmission oil cooler in the radiator and using only their aftermarket tranny cooler.   You do NOT want to do this in my opinion.  The factory cooler will provide you an additional 30% more cooling so you might as well use it!  So, the flow path will be like this:  Tranny --> stock rad cooler --> aftermarket tranny cooler --> tranny.

I mounted my cooler right to the car's radiator.  Here is a picture up under there showing the radiator and the air deflector (at bottom of picture).

Prior to placing the cooler in place, I suggest connecting your supplied hose to the top fitting.  There is not a lot of room up there once you get this in place.  I chose the top as the inlet... doesn't really matter I suppose :)  Also, my kit came with small pads that stick on the back side of the cooler.  These are not visible in the pictures but are used to keep some space between this cooler and the radiator.  This is most likely the reason why I saw no noticeable increase in engine water temperature.  (to see what this would look like in place, jump down to a later picture :)

   
Now that the cooler is in place, fasten it to the radiator.   As mentioned previously, my kit came with zip strap gizmos.  They basically are nothing more than a zip tie with a large "head" on it.  This gets pushed trough from the cooler side and through the radiator.  Once the zip cord piece comes through the factory radiator all that is left is to push the plastic holder piece on.  You can see this in the pictures above.  Also, plan where you push these through as it will make it easier on you when you have to push on your fasteners.   Once all fasteners are in place cut off the excess length so you don't have the baseball card and bicycle spoke sounds when your fans start :)

Here are just a couple pictures showing the factory transmission oil lines going to the radiator.  Notice the condition of my close to 3 year old MAC y-pipe with only its factory coating.  Not too bad, eh?   The joys of Florida and no salty roads :)

Here is a picture of the cooler mounted in place.  If you look closely you can see the fasteners used in this kit.  Oh, and I don't need to hear no garbage about how the cooler is not centered... I was anticipating my Vortech aftercooler install :)

OK, here is the actual meat of the install.   The picture pretty much labels all the lines for you.  A couple things to take notice of are:  I used the factory white hose clamp.  I also used a barbed fitting that was laying in my buds shop.  The supplied line with the Hayden cooler was a different size than the factory line.  This barbed fitting had to be jammed pretty good into the factory line because it was actually a bit too big for the factory line.   It worked though which is all that really matters.  Also notice the piece of hose I used as a protective sleeve over the Hayden cooler line.  This was done only as a precaution and probably isn't even necessary but did it anyway because the hose does pass over some metal edges.  Also, when you disconnect the factory connection you can expect to lose a little oil but not all that much.  Probably less than an ounce came out when mine was disconnected then the flow just stopped.

Run your other section of line now from the lower tap of the cooler (outlet in my case) back to the connection where the metal line goes back to the tranny.  See picture above.

Also notice how I put on another protective hose sleeve where there might be rubbing on the radiator fins.  Probably not necessary but done as a precaution.

Here are the final connections.  Notice how it all looks pretty good and fits nicely.

All that is left now is to double check all your hose clamps and make sure they are tight.   Start the car and make sure you have no leaks.  If you lost a substantial amount of oil you'll want to check your transmission fluid level as well.