Aux trans cooler

  • Need some quick down and dirty opinions...


    I have a light/med duty trans cooler... 8"x12" single row... opinions on best setup...


    1. Completely stand alone


    2. In line before OEM radiator cooler


    3. In line after OEM radiator cooler


    Going to be plumbing this tonight or early tomorrow morning. I've already drained the trans and changed out the filter.

  • Need some more info. Do you run a temp gauge? and if so, does your trans run hot all the time, or just when you put stress on it. I run a seperate stacked plate cooler from derale on a dedicated trail rig, with its own electric fan. Some guys say that you shouldnt run a trans cold all the time either, but I dont put enough miles on mine to make a difference.

  • I have a B&M external cooling a AW4. It's about 12x8. I use a thermostatic bypass to allow fluid to warm up , then it opens to cool. I like the external because it allows the radiator to perform 1 job. Much easier if you have to pull the radiator too.


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    Nobody belongs anywhere, nobody exists on purpose, everybody's going to die. Have a beer.


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  • Here goes... for the last several months my temp gauge has been acting wonky. sometimes the gauge would not work and I'd have to tap on the front of it to get it to fire up. So trying to fix that I took the gauges apart and clean the ribbon to make sure the contact was good. In order to make sure the Gage post was contacting the printed ribbon I inserted 2 small washers to make good contact. I have not had a problem with the gauges sense. From there I noticed that my gauge was running between 195 and 210 whereas before it was running 195 and below. Believing that my gauge was off before I fixed it and that the engine coolant was now running at the proper temperature on the Gage, I now noticed that my jeep was warming up much faster than it typically did. I also noticed that when I was driving that the gauge would stay at 2:10 and creep a little over that when I was idling at a light. I also noticed that the transfer case shifter boot was getting extremely hot lately. The shifter boot has always allowed warm air into the cab but it actually was getting so hot that it burnt my leg pretty bad. On my way from Chestertown 2 drop off my firearms at my brother's house, the Jeep started bogging down like it was losing fuel or flooding the carb. I let it cool down for a couple hours at my brother's house and attempted to drive it back home. I got from the outskirts of Clayton into Smyrna and the bogging problem started again. So I stopped at Advance Auto, let the Jeep cool down again, and from there made it back to my house with only one time that the engine started bogging down. So yesterday I checked the fuel Inlet float valve and cleaned it out, cleaned out the carb throat, and checked all vacuum lines for cracks but didn't find anything. There was a small peace of debris that might have come out of the float valve but I'm not sure. So to combat the extreme heat coming out of the trans, I decided to finally run an auxiliary cooler for the trans oil. I also believe that the radiator is original and is probably on the verge of needing replaced. When I experienced the volume down issue I checked the trans oil 2 see if there were bubbles on the dipstick but there were none. I'm not sure if there is an issue with the trans fluid being too hot and warming the coolant instead of allowing it to cool off through the radiator and that is what may be pushing the temp on my gauge up for the coolant. I am also unsure if the overly hot trans fluid is frothing inside the transmission causing some sort of bind up and bogging down the engine. I should also mention that while I was in Chestertown, I was out on a farm shooting but hit a few small ATV trails on the farm while I was there. That could have stuck the float valve in my carb but that still does not answer the question of why my transmission is running so hot. I do not have a temp sensor for the transmission but would like to add one sometime in the near future in order to see what the trans is running at. I would also like to add a drain plug to the trans pan because draining the fluid by dropping the pan is for lack of a better term a mess. The pic attached is the burn two weeks after it happened.

  • My vote is for inline after the stock cooler. But it sounds like you have a bigger issue and the auxiliary cooler will only be a band aid for now. Use an infrared thermometer and measure your pan temp to get an idea how hot it is getting. Tranny no likey burnt fluid.



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  • I was doing some reading up last night and there are advocates for all 3 installations.


    Stand alone- allows the aux cooler to do one job and won't affect the coolant temp or be affected by it.


    In line before radiator- allows sufficient cooling of trans oil before it reaches the radiator so it won't affect the coolant temp.


    In line after radiator- allows the radiator's larger surface to cool the oil and then further cool the oil thru the aux cooler before it reaches the trans.. good for heavy duty apps like towing/rock crawling.


    When I drained the oil, it didn't appear burnt at all... still a bright pink color and had that typical sweet smell to it. The magnet inside the pan had a little metal dust stuck to it.. very fine silty powdery dust. I think, for now, I'm going to run it as a stand alone cooler. It's easy enough to replumb the lines later if needed. I'm going to see about running a temp sensor/gauge and drain plug as well today before I refill the trans.

    Your life is made up of 2 dates and a dash... make the most of the dash!

  • This might be a stupid question, but why are you going through this whole process of trying to lower the temperature of your transmission when you haven't verified that the temperature is an actual problem? You said this whole project is to "combat the extreme heat coming out of the trans" but I don't see how you confirmed that the temps are truly extreme. Maybe the temps aren't extreme, but instead you just need to confirm the heat shield underneath is in place? What about the heat insulation inside the tub that is typically under the carpet and padding - is that still there?


    Also, through this whole thread the only thing you said you believe is on the verge of being bad is the radiator...and you aren't replacing it. Even the creeping temps when idling at a light could point to the radiator not doing its job. I guess I'm just trying to figure out why you don't start with replacing that instead of trying to add additional parts that in the end might not even be required.


    (Oh, and my vote is for plumbing the aux cooler after the radiator. That way even if the radiator is tending to heat the fluid instead of cool it, at least your transmission has a chance at receiving cooler fluid once it leaves the new aux cooler)

  • I'm not sure about the transmission diagnosis. Was it slipping big time? That's what causes them to overheat.
    To me it sounds more like a bad catalytic converter. Excess fuel can damage and plug it up. They are known to glow cherry red at times when damaged. They also kill engine power if clogged. If the core becomes loose it can move around causing plugged or unplugged conditions. Put a broomstick against it and your ear and see if it is rattling, that's a sure sign. If you have not replaced it since the last stuck needle valve incident it is the most likely culprit.

  • I just added a trans cooler to my tow rig. I put it after the in-radiator heat exchanger on the way back to the trans. Before, my transmission pan read 195 degrees, same as my coolant temp. That makes sense, there is no way it could be any cooler than the water temp.
    Now it runs cooler than the water temp. It is of course very subjective but the first time I checked after some towing the trans pan read 116 degrees. All I can say is it now runs cooler than the design value. I haven't checked it yet towing when it is hot, but I might need a thermostat on that setup.

  • Thanks for the input everyone. I forgot about coming back here to update the thread.


    Quadna- True that I haven't narrowed to issue down to the trans running too hot. All I know is that the air being forced up through the transfer case shifter boot was searing hot. The trans cooler has been on the to do list for a while but it was low priority... probably still could have stayed a low priority but it was a cheap quick mod that I thought might solve the issue since the trans is right under the flow/source of the heat. When I had run soft lines for the trans to the radiator a few months ago, I left a good amount of extra line loosely coiled at the radiator in prep of adding a trans cooler. Back when I had the trans rebuilt, the tech at Deltrans suggested an aux cooler in order to prolong the life of the trans. Right now, I do not have any insulation or carpet in the Jeep but I have also not had a heat problem this bad before since my YJ hasn't had any carpeting in all the years that I've owned it. There is a heat shield above the cat and muffler currently and while the floors do get a little warm, the main source of the heat is coming up through the transfer case shifter boot. I would definitely call the heat "extreme" if it was hot enough to cause that kind of burn to my leg. Basically the aux cooler was me finally following the tech's suggestion as well as a way to see if the 2 fluids running through the same unit were affecting each other. I was trying to rule out that possibility and a auz cooler is cheaper and easier job than the radiator. Also it was time to change out the trans fluid/filter as well so I figured do it all in one shot. It seems that your suggestion to run the aux cooler after the radiator is a popular one for the reason you stated. I've read a lot of replies from guys who ran it after the radiator and haven't seen any complaints about that set up. Right now, I just plumbed it as a standalone unit to get the Jeep back on the road. I do still have the temp gauge creeping up past 210 every now and then so there could be two causes to that but I'll mention that in a minute.


    Andy- My trans has NOT been slipping at all so I believe you might be on the right path about the catalytic converter. I never even considered it but now that you've mentioned it, I do remember you telling me about the cat when you helped me address the fuel issue and my many trips to DMV. Also the proximity of the cat in conjunction with where I am having the heat blasting through further solidifies your diagnosis. If that piece of debris was indeed sticking the float open once again and all that fuel was pouring into the carb, then it would be taxing the crap out of the cat (for the 2nd time) and has probably killed it completely now. That will be the next place that I look after my ride home from work today. I don't remember making any quick turns or stops that would allow the catalyst inside to move and block up the exhaust but it is a leaf sprung vehicle and the constant bouncing around might have been enought to move it inside the cat. I think the universal cat was ~$60ish so that won't be a hard hit to my wallet. Also when I drained the trans, the fluid wasn't burnt, was still a reddsih pinkish color and the filter wasn't horribly dirty. There was minimal metal shavings stuck to the pan magnet as well and it was silty dust.. nothing bigger in the pan.


    Now, in regards to the temp creeping on the coolant gauge... there could be a couple of contributing factors and let me know if my thinking here is logical on this or if I'm off base...


    I just installed a new fan clutch about a month back. The old one had siezed up enough that you could see the bearings in the housing so it was constantly turning with the engine. The new clutch now allows the fan to free spin w/ a little bit of resistance when it's cold. If this fan clutch was working properly, shouldn't it be fully engaged very hard to turn by hand if the engine is hot? At the moment, I am not sure if it is doing that since I have not tested it after the engine gets up to temp. I figure that if the old one was never disengaging bc it was seized up that would constantly be running cool air at full force keeping the engine from warming up quickly and keeping my coolant gauge at 195* and below. On the other hand, if the clutch is not engaging fully now, then that would allow the coolant temp to creep up past 210*.


    The coolant has not yet reached the next hash mark on the gauge past 210* and if it does go beyond 210* it is always between 210* and that hash mark. The temp only seems to creep up when the Jeep is in Drive, sometimes when idling at a light and sometimes driving down the road. If I'm idling and shift in to Nuetral or Park the temps will go back down to 210* and below every time. Also if I am letting the Jeep warm up in Nuetral or Park, the temp never exceeds 210* no matter how long it has been idling for. Now, before I messed with the wonky gauge and the ribbon circuit, the Jeep was showing that it was running @195* and below every time. It never rose to 210* at all but I have a feeling that was because the gauge posts were not making good contact with the printed circuit ribbon. The only culprits that I can see affecting the temp (now that the trans is out of the calculation) would be the radiator having restriction due to age, the water pump (less that 3 years old) or the thermostat being faulty. Could the washers that I put in between the gauge posts and the ribbon throw the gauge off? This weekend, I'll try and verify with a laser thermometer what the temps are and see if that matches the gauge readout.


    I really do appreciate everyone's help with this! I'm trying to "keep my cool" >ba dum tsss< and not get to the point of getting rid of the Jeep although it is testing my patience... again! :doh:

    Your life is made up of 2 dates and a dash... make the most of the dash!

  • also check the exhaust for a crack. Stafford had an issue at one of the flanges and it was cooking his firewall and feet. And it didnt really make an exhaust leak noise.

  • sorry to be a little late.


    You do want your trans and other fluids to actually get hot, hot enough to boil off the water that condensates when it cools.


    I always try to run the radiator (water heat exchange) first then to an air cooler.
    The water cooler is way more efficient.
    Then use the air cooler knock down the temperatures a little more.
    The air cooler don't always get the best air flow especially from the fan which we need the most when rock crawling.
    But the fan is positioned correctly to cool the radiator.
    And the radiator will help get it to operating temp faster. Some transmission will operate in worm up mode until it gets to operating temp.


    They actually sell thermostats for trans coolers.
    If you have a multi-meter with a thermocoupler you can just tap or hose clamp it onto the tranny cooler line.


    If you have A/C that doesn't work you can use the A/C condenser as cooler, free, placed perfect, and large.



    As for a pan drain.
    I always make my own. I drill a hole to let the fluid out then either just weld up the hole or weld on a nut and make a my own drain plug.



    Just my 2 cents if is even worth that much.

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