transmission cooler

**bryanrhoads77** · 09-15-2014

Hi

I have a 05 Pontiac Grand Prix with 200,000 miles and have changed the transmission fluid around 130,00 and its due for another one actually. The person before me probably never changed it at all. I had to change the radiator and put a new one couple of months ago and was curious if I bought a external transmission cooler like a TRU-Cool LPD or Haynes if I still used the transmission cooler that is in the radiator or should I bypass it?

Thanks

**Iceman6669** · 09-15-2014

Im pretty sure you bypass the one in the radiator if you get an after market one.

**bryanrhoads77** · 09-15-2014

Also what size transmission cooler should I get? I live in Ohio but the price isn't a factor since I wont to keep my car until it falls apart.

**theaceofspades** · 09-15-2014

No you don't bypass the stock one. I have a Hayden 1405 run in series. Saw temps up to 195 and that's it during the summer in traffic and I see like 160 on the highway. Totally worth the 40 bucks I paid and the 12 dollars in hardware to install it

**91parkave** · 09-15-2014

Bypass

**bryanrhoads77** · 09-15-2014

What extra hardware did you buy? Thanks

**91parkave** · 09-15-2014

Slice the rubber lines- double barbed 3/8ths fittings and fuel injection clamps. And llof course 3/8ths oil cooler hose

**buickman104** · 09-15-2014

In my experience I would not bypass the radiator. I bypassed it at first because I had a small hose leak on the radiator side. I bought a Haynes trans cooler and ran it directly to the external cooler. During the summer I was fine. In the winter I noticed on my aeroforce that the temperature never went above 100-130 and it took forever to get to that temp. After that I got a piece of cardboard to partially block off the aux cooler in hopes that my trans would run at operating temp. It was somewhat sucessful at getting the trans to the 160-175 degree range but still took forever to get there. Last winter in city driving conditions I was at a light my trans temp was still at 80 degrees and as I pulled away from a light I had slip in 1st gear. I noticed this happened only when the trans was too cold.

This month I plan on buying new lines and running them through my radiator to my auxiliary then back to my trans. That way my fuild will have no problems getting up to temp.

**91parkave** · 09-16-2014

Was this Dex 3 you were using ? Newer gp's use the dex6 which is synthetic. Which would be diffrent.

I've never had a issue even when its sub 10 degree weather.

**industrialfish** · 09-16-2014

Originally Posted by 91parkave

Was this Dex 3 you were using ? Newer gp's use the dex6 which is synthetic. Which would be diffrent.

I've never had a issue even when its sub 10 degree weather.

FYI, 05 (what OP has) came with Dex 3. 06+ Came with Dex 6.

I vote run in series because GM cars that came with an auxiliary external cooler like the Impala police car have them ran in series with the radiator.

Also, Welcome fellow Ohioan, there is quite a few of us here.

**91parkave** · 09-16-2014

Originally Posted by industrialfish

FYI, 05 (what OP has) came with Dex 3. 06+ Came with Dex 6.

I vote run in series because GM cars that came with an auxiliary external cooler like the Impala police car have them ran in series with the radiator.

Also, Welcome fellow Ohioan, there is quite a few of us here.

Doesn't matter the year you can convert to Dex 6.

Regardless you can run how you want. My logic is simple- I'd rather keep the absolutely inefficient factory brick cooler out the transmission loop. I have yet to see a case where the trans suffered from running colder as compared otherwise

**buickman104** · 09-16-2014

I have a rebuilt trans running pure and clean dex 6.

**theaceofspades** · 09-16-2014

Originally Posted by 91parkave

Doesn't matter the year you can convert to Dex 6.

Regardless you can run how you want. My logic is simple- I'd rather keep the absolutely inefficient factory brick cooler out the transmission loop. I have yet to see a case where the trans suffered from running colder as compared otherwise

Hmmm maybe I'll go to standalone

I'll see how winter goes with my torque converter lock

**buickman104** · 09-16-2014

Originally Posted by 91parkave

Was this Dex 3 you were using ? Newer gp's use the dex6 which is synthetic. Which would be diffrent.

I've never had a issue even when its sub 10 degree weather.

And i've had an issue so we are 1:1

I doubt Arizona sees as much cold ice and snow as the North East.

**eetchickn** · 09-16-2014

I put a 404 (I think) in last year in series with the radiator cooling. Check out the pics HERE.

**bryanrhoads77** · 09-16-2014

Has anyone installed this transmission pan on their Grand Prix?

http://www.ebay.com/itm/LOW-PROFILE-...-/111197690062

**industrialfish** · 09-17-2014

Originally Posted by bryanrhoads77

Has anyone installed this transmission pan on their Grand Prix?

http://www.ebay.com/itm/LOW-PROFILE-...-/111197690062

You can get a similar one made by Dorman for about $35

**theaceofspades** · 09-17-2014

Originally Posted by industrialfish

You can get a similar one made by Dorman for about $35

I think I'll get one next pan drop

**stocker** · 09-17-2014

You do an "in-series" where you include the radiator in the system. In this setup, I like to think of the trans fluid temp chasing your engine temp with some additional cooling provided by the auxillary cooler. All in all you'll likely see your trans fluid temp about 15-30 deg cooler. One upside, for those of us in cooler climates, is your radiator will help warm your trans fluid and bring it up to normal operating temps quicker during winter. This is the setup I have in my 2008.

Or you can do a "standalone" where the radiator is not included in the transmission fluid cooling. This will likely provide better cooling in the summer since your trans fluid will not be running through your hot radiator. However, you will not benefit from the hot radiator in the winter and you may find you trans fluid temps staying very low. Also, I don't know how to appropriately size a standalone setup to prevent and overheating situation.

If you'd like more information, you should be able to search out some threads. I know I've had a couple that got into some very detailed discussion. Let me/us know if you have further questions!