Mishimoto MMTC-RAM-03SL Automatic Transmission Oil Cooler, Compatible with Dodge Ram Cummins 2500, 3500 5.9L & 6.7L, 2003-2009

Works great and the fittings work fine that come with it. Easy installation and I’m running round 40 degrees cooler on average which is phenomenal.

I don’t typically write reviews, but this cooler deserves one.I have a 06 3500 drw cummins with just shy of 1200 tq. I shredded my factory trans recently due to a long haul over a mountain that out my temps well into the 220s. Then they kept climbing.I’ve decided to keep my truck automatic as my wife sometimes uses it so I went all out with a rebuild. Billet servos shift kit billet drum increased clutch capacity and a low stall billet torque converter.After I put the trans back in I blew out the factory cooler and was convinced it was okay. It was, but wasn’t enough. I was seeing cruising temps of around 200 and around 180 on highway cruising in lockup. Knowing I have a tow coming up I wanted to nip the bud and got this unit. Came fast and I am very pleased with it as a whole package.•the core is well built and much beefier than stock•installation was a breeze.•supplied hardware was great quality and give me confidence of no leaks for years to come•came with a cool penguin air freshener•lowered my around town temps to 180, no matter how hard I beat on it•towed my trailer for 20 miles just to see. Temps never saw above 190, trailer weights 9k with my car in it.To summarize, this cooler is what should have come in these trucks. It is perfect and the price does shock, but once you get it in and see the difference in temps in various loads, you’ll see why. Also, this is after all, cheaper than frying another trans.

I have a built trans in my 04. I was having problems getting temps up to 220 degrees. I bought this and that solved it. I have a coolant/atf heat exchanger delete so what i ended up doing was putting a barb on the trans and running one simple line right to the barb on the new trans cooler. I removed the thermostat and the thing stays around 150-170 normal driving. At idle the coolant temp is even lower!! When towing it goes get up to the 190s but that really isnt bad. Great product!!

Wow! This cooler is amazing. Fit perfectly in the factory mounts, hoses were easy to hook up and my trans temps came down an average of 30*. I haul an 11,000 lb 5th wheel and on a recent trip, outside temps were nearly 100* and the cooler worked great and the temps were solid and hardly ever rose even on hills.A little expensive but well worth the $$$. I would recommend to anyone who wants to protect your transmission!

I purchased this trans cooler for my 2003 Ram 3500 dually with 5.9 Cummins. I am upgrading this truck and equipping it to tow a 14K fifth wheel trailer in the mountain west. I recently had the 48RE transmission overhauled and I wanted to protect it as much as possible from heat generated while towing a heavy load. First of all, the Mishimoto trans cooler looks to be of very high quality, especially when compared to the oem unit. It arrived in perfect condition. I unpacked it from a sturdy cardboard box with the unit completely encapsulated in closed cell foam- extremely robust packaging. All kit components were secured in sealed plastic bags. I watched the Mishimoto video(s) for installation of the cooler in the truck and for installing the thermostat delete. This is a very well engineered option that is provided to the buyer in the kit that allows the cooler thermostat to be eliminated depending upon the climate that the cooler is deployed in. The cooler is shipped with the thermostat installed. Getting to the oem cooler and removing it is straightforward with the steps outlined well in the video. The install instructions recommend splicing the supplied barbed fittings into both the oem feed and supply rubber trans cooler lines and securing them with the 4 supplied hose clamps. The oem feed line on my truck was already leaking from both of the crimped ferrules on each end of the rubber line which is attached to the steel line feed line coming from the transmission. I didn't want to plumb into an already suspect line so I removed the feed line at the fitting below the check (anti drainback) valve. I used a 7/8" open end wrench and a medium size crescent wrench to loosen this fitting and the whole line came right off. Since I wanted to reinstall the anti drainback valve, I cut the oem ferrule off of it with a Dremel tool and cut off wheel. I then realized that the Mishimoto supplied cooler line might be a little short to get neatly around the intercooler tube and onto the Mishimoto cooler inlet. So I took the check valve and fitting to a local hydraulic hose supply store and bought a 36" length of high temp hydraulic hose (trans cooler line is near impossible to find at retail) and had them crimp the assembly together with a ferrule. I then trimmed it a little to length and it worked great. I reattached the valve/hose assembly to the steel feed line and used the supplied hose clamp to attach the hose to the cooler inlet. On the return side, I used the splice method recommended in the factory install video. My main concern was that I was attaching the beautiful new Mishimoto cooler hose to my crusty 16 year old oem line which has been through countless heat cycles and was pretty hard and not nearly as flexible as new line. Well, the clamp on the oem hose side did not seal up initially and it leaked. This was probably my fault. Make sure you put the hose clamps 1/2" away from the shoulder on both sides of the barbed coupler because there is a taper that prevents full clamping force. I torqued the snot out of the hose clamp and got it to stop leaking- I think. My future plan is to remove the factory return line fitting at the steel line with a $12 AC/fuel line/trans cooler line removal kit that I purchased at Harbor Freight. It works great. Going to take that fitting back to my hose shop and buy another 36" of hose and get the ferrule installed. That way I have 2 lines with no splices to reduce the possibility of leaks. Finally- how does this cooler work? With Mishimoto cooler (with thermostat installed) and the truck at normal operating temperature (unloaded) and 68f ambient,I did a 35 mile run that combined some stop and go, 20 miles of interstate at 67 mph and some divided state highway with a significant uphill grade: I got a 160-169f trans temp reading from my Banks I-Dash gauge which reads temp in the transmission valve body. (Update: just duplicated the run I described with thermostat delete plug installed and the truck ran -20f degrees cooler. Additionally ambient temp was also hotter @75f. I plan to do more testing while towing my fifth wheel and also with the cooler thermostat delete plug installed. (Just completed a 300 mile round trip towing my 14k lb fifth wheel. Trans temp on I-15 in from Las Vegas to Mesquite, NV and return was 153 to 160 f. Running 65 mph avg. speed. Ambient temp was 70-75 f.) Although the Mishimoto trans cooler is not cheap, it is a beautifully designed and built part. I look at this purchase as less than 10% of the cost of my recent transmission rebuild. I believe this cooler is going to save my trans this Summer when I am towing that trailer up mountain grades. I am really impressed with this product and would recommend it to any Dodge Ram owner that asks his/her truck to work hard.

Really straight forward bolt on and a couple push fittings. Super easy install and comes with the option to bypass thermostat which I did. Dropped 30 degrees on transmission.

This is a expensive replacement but purchased due to higher capacity and perceived easier installation. I am concerned with the hose connection points to the heat exchanger. They appear to be plastic and the first time I installed the hose and tightened the clamp the hose rotated on the fitting when training the hoses into position. Not very re assuring. Retightened sever times. I would suggest a more robust braided hose assembly with solid threaded connectors.

Installation was easy, fits good, work’s excellent