Aftermarket Transmission Cooler Mounting on 4th Gen Truck

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NicksGarage

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My 2009 1500 4x4 is intermittently having a problem with the transmission overheating when towing. Mostly when I'm towing, it's hot outside, and I'm in stop and go traffic or climbing hills. I recently went on a 1000+ mile camping trip towing my 3000 pound travel trailer and didn't have a problem. Drove 30 miles towing my empty car trailer and got stuck in construction traffic and transmission heated up enough to go into limp in mode. Last time was towing travel trailer 100 miles and once I got in slow traffic on the freeway, in 105 degree heat, the transmission went over 260 degrees according to the gauge and went into limp in mode. Stopped and ran it in neutral until it dropped to 180. Hit the road again and was fine until I got into traffic again. Eventually it just wouldn't cool down while towing the trailer and couldn't get up a hill. Disconnected the trailer and got it cooled down under 200 and it drove ok. Had the truck towed home. It's driving fine and no transmission heating issues driving around.

The cooler is part of the A/C condenser and I can't tell if it's flowing enough. Doesn't matter if the A/C is on or off and the truck has a mechanical fan.

I want to put in an aftermarket transmission cooler with a fan and see if that fixes my problem. There isn't much structure there in front of the radiator so I'm curious to see how other people have mounted coolers on these trucks. I'm ok with fabricating brackets if needed. I've seen some people mounting coolers under the truck next to the frame but I'd be worried about rocks hitting it or the fan.

Thanks for any replies.
 
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NicksGarage

NicksGarage

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Didn't get any answers and haven't found much online, so I'm figuring it out myself. Not enough room behind the grille and originally, I thought I was going to put it under the body along the frame rail along the passenger side. This location isn't going to work as the cooler barely fits in there and wouldn't have good access to the fittings. With the truck up on the lift, I found that there is a lot of room behind the bumper under the radiator. Will need to add some struts between the frame rails to hang the cooler from. Thinking of using some 1x2 rectangular tubing since it has to span 32" between the frame rails. If I need more air flow, I can drill some holes in the plastic bumper filler. But I'm thinking it will be fine without since the cooler has a fan, and I don't want to cool the trans fluid too much.
 

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crash68

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Does yours have the 6 spd or 8spd with the shift knob?
'13 was the first model year for the ZF 8

The OP probably needs to install one of the RFE thermostat bypass blocks.
 

Wild one

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'13 was the first model year for the ZF 8

The OP probably needs to install one of the RFE thermostat bypass blocks.
The OPs truck is an 09,i don't think they were using the thermostat block on the real early 4th Gens,i don't think it came into play until somewhere around 2013 when they started implementing the thermal management system
 
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NicksGarage

NicksGarage

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It's a 2009 hemi with the 545RFE 5-speed trans. Doesn't use the bypass block. The factory transmission cooler is combined with the A/C condenser. With the cooler behind the bumper, it won't get much airflow so it shouldn't overcool the transmission. Then the fan will pull air through the cooler if needed. I can always open up the plastic filler in the bumper to get some additional air there. I should have the install done this week.
 

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NicksGarage

NicksGarage

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I got the cooler installation done and everything plumbed and wired. No leaks, which worried me. I thought maybe the factory cooler was plugged and restricting flow. But it just turned out that I didn't have any leaks. I live in a mountainous area and did 3 test loops up the hill on the windy mountain road, about a 2300-foot elevation change. I had my 2800-pound car trailer attached.

The transmission fluid goes through the factory cooler first, then to the new cooler before returning to the transmission.

First trip up the hill was just the cooler, without the fan running. Fan wired to an external switch, bypassing the thermal switch on the cooler. Outside temp was 85 degrees and at the top, gauge on the dash got as high as 181 degrees. Turned the fan on with the switch and went down the hill. Temperature on the dash went down to 150.

Second trip up the hill was with the fan on the cooler turned on. Starting out at 150 degrees on the dash, at the top, temperature only got to 159 degrees on the dash.

Third trip, I connected the thermal switch on the cooler. It's supposed to turn the fan on at 180 degrees and then off at 165 degrees. Outside temperature dropped to 75 degrees. Temperature on dash got to 172. Fan did not come on. Let the truck idle and temperature on dash went up to 194 degrees. Fan did not come on. Used a laser temperature gun on the inlet and outlet on the cooler. Inlet temperature on the fitting was 168.8 degrees. Temperature on the outlet was 144.2 degrees.

When I read reviews on this transmission cooler. Many people complained that the temperature switch didn't work right. Maybe they weren't measuring the temperature at the cooler itself.

When the fan is running on the cooler, it is pushing a lot of hot air.

Next week we're going on a 600-mile camping trip towing our 3000-pound travel trailer plus our gear. Temps aren't supposed to be too hot, but the route can vary 40 degrees during the day. I won't know how traffic is until we're in it. I think I'm just going to use the manual fan switch and watch the dash gauge. I don't want to over cool the transmission and don't want to have to pull off the highway to crawl under there and switch the wiring.
 

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Lyle Longboat

2011 Ram 1500 5.7 Sport CC
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I have the 2011 with the 545rfe…. I threw on a Hayden aftermarket trans cooler and did not by pass the Rad. I have mine tucked behind the front grill to the driver’s side. It’s bolted to the top cross member and lower cross member using brackets I fabricated, not hard at all. Just ran send and return lines and it’s all good. I also grabbed a bigger trans pan and used redline C+ Trans fluid. It worked with keeping temps down… then she blew twice for other reasons lol. But it’ll keep your trans temps down good.
 
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Well this didn't turn out as I expected. After several test drives and having no problems with the new cooler over-cooling the transmission, we hooked up the trailer on Tuesday to head out for our camping trip. Got a mile from home and all the gauges went dead, wipers started going, headlights came on and just about every warning light on the dash lit up. Front windows wouldn't open but rear ones would. Fortunately, truck still ran so we turned around and went back to the house. Did some looking around and it seems like there are a million possible cause for this condition on this truck. Swapped the battery to see if that had any affect and it didn't. Note, that my transmission cooler fan is only connected to ground and the positive batter terminal, not to any factory wiring. I guess the truck just doesn't like to go camping.

Wasn't going to miss the trip so I rented a 2019 RAM 2500 Bighorn 4x4 with the 6.7L Cummins from TURO. It of course handled my 3000 pound travel trailer with ease and much better mileage than my Hemi truck. Now I have to figure out what's wrong with my truck. I suspect the TIPM is the place to start.
 
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Replaced the TIPM with a new one from Dorman and all is well again. Towing a car up the mountain on my car trailer tomorrow so I'll see how the trans temperature goes. A nice hot day too.
 
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NicksGarage

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Success today with the transmission cooler. Picked up a 1960 New Yorker parts car down the mountain. Outside temperature in the morning was 71 degrees. Didn't run the cooler fan and the dash showed the trans temperature getting up to 147. By time I got the car loaded, it was getting up to 90 degrees outside. I waited until the trans temp got up to 192 and turned on the cooler fan. Quickly dropped down to 162 and turned the fan off. By time I started going up the mountain, the outside temperature got up to 96 degrees. The trans temp got up to 191 before I turned the fan on again. It dropped to 172 by the time I got home.

I'm bypassing the temperature switch that came with the cooler because the fluid temp at the switch is lower than what the dash is showing so the fan wasn't coming on when the truck indicated the trans temp was above the 185 degree trigger. Didn't want to find out how hot it had to get to actually turn on. That will be a test for another time.
 

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Wild one

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Success today with the transmission cooler. Picked up a 1960 New Yorker parts car down the mountain. Outside temperature in the morning was 71 degrees. Didn't run the cooler fan and the dash showed the trans temperature getting up to 147. By time I got the car loaded, it was getting up to 90 degrees outside. I waited until the trans temp got up to 192 and turned on the cooler fan. Quickly dropped down to 162 and turned the fan off. By time I started going up the mountain, the outside temperature got up to 96 degrees. The trans temp got up to 191 before I turned the fan on again. It dropped to 172 by the time I got home.

I'm bypassing the temperature switch that came with the cooler because the fluid temp at the switch is lower than what the dash is showing so the fan wasn't coming on when the truck indicated the trans temp was above the 185 degree trigger. Didn't want to find out how hot it had to get to actually turn on. That will be a test for another time.
Isn't the cooler fan switch adjustable?
 
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