Hayden Automotive 678 Universal Rapid-Cool 9.5” x 11” Add-On Transmission Cooler – Not for Direct Replacement of the OE Cooler

First of all, the quality of the radiator itself is very very solid and well made. The heat sink fins are not too thin like many other aftermarket coolers. It’s very well made, and I’ve always had great luck with Hayden products, like their fan clutches, and transmission fittings.I originally bought a Chinese knockoff 40k trucool transmission cooler and I had to return it even before I even put it in my truck because of how poor the thickness of the radiator fins were. I could literally bend them with my finger nails. Did not feel comfortable about putting it in my truck. It was a massive leak waiting to happen.So I bought this Hayden cooler. It was actually cheaper than the 40k knockoff, and it’s much stronger and better built. I will be installing this tomorrow.EDIT: I installed these 2 days ago. Install was very easy, it look me about 3-4 hours because of all the custom mounting brackets I made, and all the hose routing with protective looms on it. But install was very easy and straightforward.I’ve been driving for the past two days with my scan tool hooked up to monitor the transmission temp, and I’m very happy to see that my transmission temperature does not go above 165F, even in slow stop and go traffic. Before I installed the cooler, my transmission temperature temp used to be around 190F-200F, but I’m glad to see how much cooler it is after the install.Very happy with the results, and this modification will definitely make my transmission last much longer.

Added this to my GX470 paired with a Goliath Offroad mount. Took no more than 30 minutes to install and have been performing flawlessly. Definitely see about 10 degree lower trans temps with this installed. I would say it was a huge upgrade for hot summers/mountain passes that I encounter. Large effective cooler.

I cannot say how I truly feel about this unit seeing it has only been installed for 2 weeks, but the mechanic that installed it stated it was a good model and brand. Stated it would do the job on my 1990 Chevy Silverado 5.7L engine with 4 speed trans. The internal cooler in the radiator ruptured and got water in the trans and flat ruined it. So I NEVER want that to happen again so I decided on and external one for my truck. I trust my mechanic and believe this will keep it cool and will NOT have another episode of water in the trans. Stated it was fairly easy to install and fit on the A/C cooler using the supplied hardware. Fits snug and so far so good. If you are looking for a external trans cooler I will recommend this one as my mechanic gave it a Thumbs Up..

Worked great on 08 Silverado lifted with big tires so trans ran hot at 215 constantly now it stays at 180

Just enough cooler for my Acura MDX with the stock cooler bypassed. Made some aluminum brackets to keep the cooler off the AC condenser. aftermarket temp sensor peaks at 65C in Heavy FL traffic.If I had to do it again I would have went one size larger 679 just for a little extra insurance.Update: 7/11/2017No fan, 100 degree day in stop and go FL traffic temp sensor hit 82C not towing, flat terrain, and AC ON of course. that's 180F and within 10 degrees F of the fluid limits of most transmissions. Next vehicle I will definitely go larger or possibly add a fan to this cooler.Update2: 9/26/2017added a "9" Inch Electric Radiator Cooling Fan 12 Volt Adjustable Thermostat Control Kit" before towing on a 2500 mile round trip from FL through OH for a week and back through GA. First, a 9" fan is too large for this cooler. Suggest a 6-7". The thermostat kit was set to 60C/140F using my aftermarket digital temp sensor on the trans output line BEFORE the cooler. Towing a single axle open trailer with an UTV on it totaling 2000 lbs. Highway temps in 96F FL/GA trans fluid temp 67C/152 using D4 on the transmission. First big 10 mile hill on I77 in VA heading north 62F outside temp with trans temp of 87C/188F. Later in the same day; outside temp 80F, stuck behind a tractor trailer at 40 mph, up a steep 1 mile hill, 2 lane road I hit a max trans temp of 101C/213F. Most consider this to exceed the max temp of transmission fluid and require a full fluid change.Next year I will be reviewing the 679 version. This cooler is not quite up to the task for summer hilly towing even with a fan.update3: 7/10/2020: Lost the cheesy knob for temp control even though I glued it on. I had it set already where I was happy and still hear the aux fan turning on from time to time. the fan I use: American Volt 12V Electric Radiator Cooling Fan