Tranny Cooling Lines

botamac · May 2, 2008

I have a 2007 siverado wt and would like to install a transmission cooler. I would like to know the best way such as (1) install it by itself stand alone, or (2) with the one in the radiator? witch line is the return, the one on top or the one on the bottom of the radiator?

Thanks for your time.

08 Sierra Z71 · May 2, 2008

A few years ago, I installed an aftermarket transmission cooler on a '94 c/k 1500. I don't remember every little detail, but if I remember correctly, to determine which line is the supply and which one is the return, wait until the engine and transmission are cold. Start the truck, put your foot on the break and put it in gear for about ten seconds. Next, kill the engine and feel the transmission lines. There will be a big temperature difference. The hot line is the supply line.

C & A s Dad · May 3, 2008

The above method will work but I like to use 2 people. Have someone in the truck start it while cold and you are holding both lines. Have them put it in gear and the line coming to the radiator will heat up first. The other line will be the rtn line which is coming out of the radiator back to the trans. IMO and all Mgfs I know of agree with this, you need to install the aux cooler in conjunction with the internal cooler. You need to use the line coming from the radiator to go to your cooler and then from the cooler back to the trans. This the way GM truck equipped with a factory cooler would be done.

I would like to know what kind of climate you live in so I can help you with the size of the aux cooler. If you live in a really warm climate as I do, you should go with a 11" x 11" x 3/4" model and only get a stacked plate style cooler. Compared to the old tube and fin style they are much more efficient and do not effect flow nearly as much. Our (CARQUEST) supplier is Hayden and this cooler is a 77423. If you live in a climate that sees some really cold temps, step the size down to a 9"x 11" x 3/4" or maybe even to a 7" x 11" x 3/4". These coolers are so efficient you could over cool the fluid if you live in a really cold climate, This is why I recommend stepping it down in size. There are other brands out there but you can find Hayden at a lot of places. The # I gave you is specific to CQ and a Hayden branded unit will have a different #.

One last thing. You will find some stacked plate coolers in a 1.5" thick models. While these are still good units, they are not as effiecient as th 3/4" thick models. GM realized this in 99 and stop using the thicker models. I have also talked with an engineer at Hayden and he said this is why they stopped using the thicker models.

If you want some pics of mine installed. PM me your e mail and I can send you about 8 good shots.

CapitalTruck · May 3, 2008

Get the tranny cooler from gm accesories, install it in series with the one in the radiator. The tranny cooler from GM accessories is like the factory cooler that comes with the trailer towing package. Its a good one. On the radiator tranny cooler the top connection is the output one (tranny fluid returns to the tranny from that line). So, if you install another cooler, run it from that connection (the top one) to the cooler you install, then from that cooler back to the transmission. This will prevent transmission fluid from being cooled in your installed cooler and then running through the radiator and being reheated.

--Jeremy

C & A s Dad · May 4, 2008

There is certainly nothing wrong with the OE cooler. It is a stacked plate design cooler. However, I removed my OE cooler and opted for something a little bigger becasue the temps where I live can reach 100+ in the summer and I tow a 6500 lb camper. If he lives in an area similar to where I live and is towing something heavy, it would be my opinion that he should move up in size a little. The stacked plate cooler that Hayden offer is identical in design to the OE cooler. If I am not mistaken, all of these sp coolers are made by a comany called True Cool.

botamac · May 5, 2008

I live in Michigan so some days are warmer then others, my biggest problem is sitting in traffic and not moving very fast and hence not a whole lot of air moving though the front end of the truck, yes the power fan will come on when needed to cool the radiator. But when the fan is not on what is going to cool the trans cooler?

C & A s Dad · May 6, 2008

All aux trans coolers are a surface to air cooler meaning the hot surface of the cooler being exposed to cooler air will reduce the temp of the fluid running through it. There are units out there that are self conatined. Hayden makes a unit with a 10" e fan mounted to a stacked plate cooler. If you truly operate at idle a great deal you may want to look into this. However, they are not as efficient when moving down the road becasue the e fan will block some of the air flow.

My suggestion would be to install a 7 x 11 x 3/4" or 9 x 11 x 3/4" stacked plate cooler and you should be in good shape. This unit would be 2" to 4" taller (depending on which one you use) than the OE unit that would have come on your truck if you would have had the factory tow package.

botamac · May 7, 2008

Thanks C&A I'll give it a try, now all I have to do is find the room/

C & A s Dad · May 7, 2008

Room is not an issue. You have an "A" brace in front of the radiator. This is where the OE unit is mounted.

If you send me your e mail address, I can send you about 7 or 8 good pics of how I installed mine.

yukondan · May 7, 2008

Adding a Tranny Temperature guage is as important as adding a external cooler. By watching the temperature change you can change your driving speed or pull over to keep from burning the fluid and eventual trans. problems.

On my '01 Yukon with the 4L60E it was a simple deal of purchasing a guage cluster from a 1500 series HD that has the Tranny guage. Then it was just plug and play since the 4L60E already has the temperature sensor mounted in the valve body of the Transmission.

Do a search on the forum for members doing a cluster swap and even some just purchasing a aftermarket tranny guage and installing it in their current guage cluster.