Trans Cooler Return Line

IMFLYN · April 11, 2008

I am installing an external trans cooler on my '07 Classic. It has the 4.3l v6. I did a search and found conflicting answers, maybe because of year/ engine differences. Is the return line to the transmission the top or bottom line coming out of the radiator?

Thanks

C & A s Dad · April 12, 2008

This can vary by vehicle but I can tell you how to tell for sure. You have two choices and the first will be the easiest.

With the truck cold, open the hood and place a hand on each line going into the radiator. Have someone start the truck with the emergency brake on and place it in reverse. It will begin to warm the fluid within a minute or two and the first line that begins to warm up is the line coming from the trans and the other is the rtn line coming where the fluid comes out of the radiator.

You seond option is to disconnect a line and start it but just know it will spit a good bit of fluid very quickly.

A good Tech could likely tell you from experience and I can tell you which line is the rtn line on my 02 but it may not be the same as yours.

Hope this helps.

BTW, you are doing the right thing installing a good aux cooler. Hope you got a stacked plate style cooler, they are the way to go.

IMFLYN · April 12, 2008

Thanks. I tried feeling the lines and MAYBE the top one was cooler but it was hard to tell so I'll try the top first and see if I chose correctly.

I got a B&M 14400 btu cooler, stacked plate. The other day just running errands on a 65 degree day the trans temp got up to 195. The only thing I was hauling was myself and my wife!

Mikeee · April 12, 2008

... Hope you got a stacked plate style cooler, they are the way to go.

X2

C & A s Dad · April 13, 2008

Peter, the B & M is a stacked plate cooler and even though it is likely a 1 & 1/2" thick model you should be fine. The thicker coolers are not quite as efficient as the 3/4" thick models but they are still great coolers.

IMFLYN · April 21, 2008

I installed the cooler today. The top line was indeed the return line. Here are some pics of the install. I flipped the crossmember upside down and drilled an extra hole in it for a mounting point. I also had to notch it for the hose. The top screw I hit with some black rustoleum. After the grill was put back on you don't even notice the cooler. The grill come on and off very easily. Just 6 snaps holding it on. The lines I spliced into the return line. I know, I know, it needs 2 more clamps. I'll pick some more up this evening when my wife gets home. After I get a chance to drive a mile or two I'm going to change the trans filter too; just in case some dirt entered the system. The truck only has 14k miles, so I call it a break in change ;) Also included are pics of the Interceptor scan gauge I installed last fall, and a happily freshly waxed truck.