Transmission coolers

The idea of a tranny cooler is a good one. Keep the transmission running cooler and it will last longer. Fluid stays cleaner and parts last longer. Those are theories. The problem is that Grand Prix don't have a problem with transmission temperatures. A tranny cooler might be a great idea on some cars but the Grand Prix is not one of them. Little known to most is that the GP PCM monitors transmission temps and if the tranny temps get too high the PCM will set a check engine light and possibly take precautions to limit abuse.

Here is a quote from INTENSE racing (they build performance transmissions for GPs) "Should I run a tranny cooler?”

“Only if you're planning to pull a trailer through the mountains. Otherwise, we recommend against it on vehicles with the 3800 FWD/4T65E drivetrain. “

We have dissected more of these trannies than anyone else in the performance after-market, and we have yet to see a single heat-related failure. Hard parts break in these trannies, and these failures will not be prevented by a tranny cooler."

We have also done dozens of transmissions here at ZZP and we know from opening them up that a tranny cooler is not helping anything. We've seen tranny's break with 50 miles on them and others with 125k on them. Problems have NEVER been related to fluid temperatures or fluid break down.

We are at the point where we can't convince our customers to take off their trans coolers or not to buy one, we often hear the response "well, it can't hurt" or "I'll just play it safe" Wrong! Transmission coolers have many down sides. Going back to the opening of this article we broke down all the reasons not to buy unneeded mods but the tranny cooler is especially dangerous and here's why:

We have had to rebuilt more than one tranny due to a failure of a tranny cooler. When your cooler leaks it can cause very serious problems. Below is a pic from a car in Grand Rapids where a severed line left this owner in the cold.

Here is a quote from a member of the RegalGS forum:

"I installed the GM cooler 10 plus thousand miles ago along with the Thrasher shift kit. (second setting) I'm a bit "old school" when it comes to these things. I figured if the cooler is on the Police Impalas, it would work with the GS trans nicely. Further, I do have a hitch on the car and haul a small trailer on occasion. For me, I feel more comfortable in using a cooler.

However, during the installation, I double clamped the lines and triple-checked for leaks. There were no leaks and the installation worked great for a while...until...on a WOT jaunt up a back road on my way to an appointment, I noticed a bunch of smoke behind the car. I stopped and looked under the car and noticed fluid pouring out of the front of the car. I thought it was antifreeze and traveled another two blocks to the appointment where I finally opened the hood. FIRE! I carry a fire extinguisher in the trunk and the fire was put out quickly. There was no damage from it either, thank god!

It turns out, one of the "double clamped" lines blew of the steel line and sprayed trans fluid all over the exhaust manifold. Fortunately, I was two blocks from the dealer. Still, I had it towed, I didn't want to risk more fire and a bad trans. The dealer replaced the lines and flared the ends so the re-clamped rubber lines wouldn't come off again. Just a little story of my experience."

With nothing to gain and a lot to lose, you can see why we are so strongly opposed to tranny coolers. Even if the cooler doesn't fail you are adding weight to the car, costing yourself money and blocking some of the airflow to the main radiator which in turn makes the car run hotter costing you HP. If you have a car in a very hot climate or car with a turbo kit, we suggest our oversized radiator to properly take care of the heat issue.