Installing Transmission Cooler on a 99-04 Jeep Grand Cherokee

The Transmission cooler came out of a 1990-1994 Ford Explorer. This can be done in 1.5 hours. List of parts. Transmission cooler $12.00 junkyard price. 5 foot 3/8 Transmission cooler hose $10.00 4 hose claps and 3 bolts. I used M6x1.0x20mm bolts that I had lying around.
Hayden Automotive Rapid-Cool Plate and Fin Transmission Cooler amzn.to/2IvJgi4
Superchips 42050 TrailDash 2 Programmer w/Mileage Coach Software TrailDash 2 Programmer amzn.to/2xUOv4l
Facebook / martinbuilt-2351766611...
#martinbuilt #jeepgrandcherokee #jeepgrandcherokeeupgrades

[@TurtleMasterFlash]

Thanks for taking the time to make this video. Great job and excellent information.

[@matty86suk]

Cool seeing the numbers, good vid! I've used a Ford Explorer trans cooler on my xj, looking for something bigger for my zj.

[@robgoffroad]

This has been on my TODO list for some time. Now I'm definitely going to do it as soon as I find the cooler I bought for the task. It's buried in the shed someplace.

[@martinbuilt]

I know what you mean, I have so many thing that I have bought for my Jeeps and haven't gotten around to it.

[@PennIsMightier1]

WJs did have a factory aux external transmission oil cooler early on. Later on they put the power steering fluid cooler in the same spot with basically the same cooler flipped over so the lines ran the other way.

[@RDJL559]

Thanks for the reply... Great videos, I'm subscribing now

[@moldyapples]

This is from the factory service manual: "Because the internal oil cooler is so efficient, no auxiliary oil cooler is offered" I guess the manual writers haven't been to Las Vegas in the summer! (or Phoenix, or...)

[@laragreene8328]

There are original parts, that wear out , you can replace if transmission over heats though,right!

[@squirrelcommander]

Hey Martin, have you thought about doing an aux engine oil cooler? I’ve wondered if it can help with engine cooling.

[@EthanOpdahl]

The Hayden Cooler listed is too big, you need a rectangle shaped one, find the one that is 6" x 11" ( 7" max width ), Rapid Cooler Part #: ATP 17508. Also, suggested to install in series, meaning keep the fluid going through the main radiator, then feed out to the trans cooler and back to the Transmission last. Should be cooler overall. I have not tested to verify.

[@JF32304]

I've done this to one of my WJ's and about to go and do it to the last WJ here that I picked up the other day. As well as the electric radiator fan (this is a must).

[@martinbuilt]

I'm glad you liked it and found it helpful. Yeah I've done the electric fan and deleted the hydraulic fan and love it.

[@JF32304]

@@martinbuilt I know why they did the hydraulic fan, but it was a mistake. Electric is the way to go.

[@MegaDmachine]

With today's temps I use both on my wj

[@boogerhead0]

Years after, did you ever connect in the default radiator trans cooler into your add-on cooler? I happen to have my '04 apart at the moment, it does have an aftermarket trans cooler in front of the condenser, and it is in series with the radiator cooler. This would seem to me that the trans fluid would be heated to engine (radiator) temp 'all the time'.. and heat from the cooler in front of the radiator would also be added into the airflow going by the radiator tubing directly behind the add-on cooler. I am definitely impressed with the temp drop with the add-on cooler, but here, we are in a more temperate range than you, in winter, down to about 0F worst days, and then 102F ambient, summertime.

[@Gabrielggfloripa]

hello, what app or ob2 system do you use in your cherokee, I need to see the ABS and airbag failure, which in Brazil I didn't find an automotive scanner that gives correct information! Thanks

[@Ink4Breakfast]

Hey martain, can you do a quick video on checking transmission fluid level and topping it off after removing trans cooler lines. 99-04 Jeep Grand Cherokee 4.7L (WJ) Mine is an 02 Laredo with Selec-Trac JHD-242

[@tewatenebillemery5584]

175f safe temper.thanks for tips

[@susu-mi7kx]

Martin, I asked about this, and you told me the line closer to front of transmission goes to the top line of the radiator. Problem is on my grand cherokee WJ 4.0 6 cyl. the two lines sit on top of one another against transmission clamped against with a clip, like a brakes lines are held. and like in this video those two hoses you show, the way they connect to that line, one of those lines on mine has i believe a check valve connected to one of those lines and then the skinny hose. how can I email you a pic. i really want to finish this job and drive off

[@WJsLifeonaBoat]

Hey man, been watching your videos, really good stuff. I wonder where the TrailDash reads the temperatures from for the transmission. I have a physical sensor in the pan on my 2004 WJ Overland. I used to be getting 200-205 pan before the aux cooler and now after the aux cooler install I do not see transmission pan temps over 170 on the hottest days in traffic, 95-100 degrees ambient. Running highway it'll hover at 150 same 95-100 ambient. Also your coolant temp is too hot for a 4.7, need to bring those down to 195. Is your hydraulic fan kicking up?

[@martinbuilt]

Snobrdrkid07 I don't know where the actual sensor for the transmission is. I haven't actually looked into the operation of the hydraulic fan is it supposed to kick into a higher speed? I do notice that it does run around 220 plus degrees on days that are 108 degrees or hotter here in Vegas

[@WJsLifeonaBoat]

Hey Martin, I actually don't know where the sensor is either, but the pan temperature is the "average" temperature. There are spots that are probably hotter. It was 100 on the east coast with what might as well be 100% humidity and running 200 coolant and transmission pan temp was 155 running down the highway. I still have my factory cooler hooked up for the transmission as well as the auxiliary cooler. When I am sitting in traffic and the AC on, I can feel the hydraulic fan and hear it, it is spinning so fast. I'd check the water pump out, and maybe consider a new radiator (of quality) if it is original. I wouldn't feel good driving down the road with those high numbers on a 4.7

[@intreppid]

The hydraulic fan runs off the power steering pump, as the pulley on the pump spins faster it pushes more fluid thru the hydraulic fan and makes it turn faster. Usually once you are driving about 50 mph or so the air forced thru your radiator is sufficient to keep your water temperature correct.

[@WJsLifeonaBoat]

intreppid this is partially incorrect. The fan speed is controlled by a solenoid that will let more or less fluid flow at any speed. At idle the fan is capable of spinning very fast and if you do rev it, it will soon even faster with additional fluid flow.

[@martinbuilt]

the fan does kick up when I turn on the A/C. I can't tell if it is when I'm drivivg

[@berniesoprano6980]

So do you leave the old lines in place? And by chance, do you have a part number for the unit you installed? Great video. Thank you.

[@martinbuilt]

Jose Martinez Yes I left the lines coming from the radiator in place with the bolt stuck in the end of the lines are still there today. I got the transmission cooler out of a 90-94 Ford Explorer..Thank you!

[@scotth3625]

Hey I know this is a old video...but will Superchips 42050 Traildash 2 give me a Trans temp reading on a 2001 4.0l Grand Cherokee through the data port also? Or did you install a trans temp sensor in the oil pan?

[@pistolmike791]

Hey if you see this, have you had to replace the trans lines at trans itself? The ones that run above the exhaust? I cannot find the lines anywhere and I need them. Popped one the other day

[@susanfrazer4341]

good job brother

[@martinbuilt]

Thank you

[@jamesreeves179]

My 04 JGC 4.0l automatic with the select-trac seems to be using the top portion of the AC condenser not the ports in the radiator.

[@martinbuilt]

You may want to have another look at that in 2001 with the 4.7 L they started putting the power steering pump cooler integrated into the top portion of the condenser.

[@TyRich26]

Hey Martin, what super chip are you using for the transmission temperature read out?

[@martinbuilt]

trail dash 2

[@pennypackmtb2542]

I live where it gets colds and I'm now installing a Transmission Cooler Thermostat.

[@martinbuilt]

That's probably a good idea. In my 98 Jeep Cherokee, I have bypassed the radiator trans cooler and during the winter months the temp never even gets close to normal operating temp. If I drive at highway speed it won't even get to 105* on the digital gauge. Not until I slow down and the torque converter is unlocked will the temp come up.

[@bolshoibooze8010]

​@@martinbuilt on my 96 zj, I ran 1/2" hot and return lines in my 44re that spliced into 2x 3/8" system with Y-barb connectors. 1 goes directly to radiator and the other to a 12x14" trans cooler with fan in the back of the jeep which has a 3/8 barb joint with a valve. In the winter I shut the valve off, trans temp ran directly from radiator gets 170. Turn valve half way in spring and fall, fully open in summer. Went to Death valley last year 125F weather and my trans fluid temp only gets 185F crawling on dirt.

[@nathanstout7763]

Is that 5/16 hose or 3/8? Doing the cooler hoses on my buddys today after work need to get some hose and clamps for it. I know i need about 2 feet of whatever size it is.

[@martinbuilt]

It was 3/8 diameter

[@Ink4Breakfast]

I had mt radiator blow a leak when uninstalling a scary unsafe electric fan that was installed by a shop mechanic without controller, module, fuse or a relay. It was hard wired to the battery. Now i gotta change radiator to a Denso which im told is factory $187 And i have no clue how to check transmission fluid level after disconnecting cooler lines. The holes in dipstick dont give a clear indicator of correct fluid level. What operating temp you need to be at. If i can check the fluid level cold before disconnecting then swap radiator and top off to that exsact spot. Then flush rad and bleed coolant and run to operating temp and double check fluid level. If you can specify what dots it should he between cold vs hot that would help a lot

[@intreppid]

Great video's Martin. I am the original owner of a 2004 Grand Cherokee 4.7., 145,000 miles. I have a cross threaded spark plug in the #7 hole ( drivers side all the way back). Any suggestions on how to drill and Heli-coil it or is that for a shop ?? I am an old school hot rod'er and shade tree mechanic. I did recently replace the rear main engine seal in my garage ( that was a job ) ! Thanks, Billy

[@martinbuilt]

That sucks...I was getting ready to change plugs on my and do a video. I wounder if you can get a tap down there and clean up the threads. then vacuum out the cylinder. Then if you can get a bore scope to see that the threads look good and that you got all the shaving out.

[@peterbarrego2916]

helicoil kit

[@MrKaycleans4u]

What did you do with the other lines you plugged with bolts? The original lines that came out of the radiator?

[@martinbuilt]

Well I've been running that cooler now for 2 years I believe with it disconnected from the radiator transmission cooler. it's been working perfectly fine that way so I am going to just remove those lines from the radiator. I only left them there just to make sure I didn't need to hook them back up if you live in a cooler climate I would recommend that you use the radiator transmission cooler and the auxiliary one. Go through the radiator first then the auxiliary.

[@steelerdynasty2007]

@@martinbuilt I'm in FL, so obviously not a cooler climate....BUT, i just don't want loose/plugged hoses flopping around (i think the mod looks great and wouldn't want to ugly it up by having hoses that don't connect). Could you explain a bit more how to connect both? Which one (upper or lower) is "in" and which is "out"? I imagine i could figure out how to connect both properly. I'm thinking something like this: 1. disconnect the current "out" hose from the transmission end (the hose that runs FROM the radiator TO the transmission) 2. reconnect this same hose to the "in" (upper or lower?) of the transmission cooler 3. connect a new hose from the "out" (upper or lower?) of the transmission cooler 4. connect new hose FROM transmission cooler TO transmission is this correct?

[@martinbuilt]

@@steelerdynasty2007 the transmission line that connects to the highest point of the radiator is your return line. Disconnected below where it turns to rubber hose. Then connect a rubber transmission line from that point to the Lower Side of the auxiliary transmission cooler. Take another rubber transmission line from the upper auxiliary transmission cooler and connected to the metal line returning to the transmission that you disconnected earlier.

[@ronr149]

So there is a total of four lines for cooling. Not sure what the the two you capped off were for. Im rebuilding one of these and im getting to the transmission lines next. Any input would be helpful!

[@martinbuilt]

There are 2 trans lines, supply, and return. The 2 that I capped off were from the trans cooler that is in the radiator. I bypassed that cooler. Then you have the supply and return from the transimmision. If you want to use the radiator trans cooler in series with the other cooler leave the supply line (hot fluid) hooked up. Then take the return line from the radiator to the secondary cooler and the return line to the other side of the secondary cooler.

[@ronr149]

@@martinbuilt much appreciated. Your videos are top notch!

[@martinbuilt]

@@ronr149 Thank you. I really appreciate that.

[@magiclydelicious1]

Ive changed a raditor on a 4.0 and like to never got the lines loose from the raditor because they hadn't been off in so long. An external trans cooler should have been a factory upgrade.

[@martinbuilt]

Absolutely, heat is the number one failure for automatic transmissions.

[@nebulousJames12345]

Did you fill it with transmission fluid after you connected the new cooler? Do you need to fill up the cooler?

[@martinbuilt]

No, you will lose very little fluid and the cooler only holds a few ounces of fluid. You could add 8 oz if you what to.

[@jorgecantusosa5106]

Would the 2 lines in the description work on a 4.7 Jeep wj radiator

[@martinbuilt]

All the work was performed on a Jeep with a 4.7

[@susu-mi7kx]

can you help a girl out.... so I have a 2001 grand cherokee laredo 4.0 6 cyl, it uses 4 oxygen sensors( if that means any thing). I had to replace the radiator, and the long and short cooling lines were siezed on them, so I removed then from the rubber hose they attach to. so that I could remove the radiator(The cooling lines I have ,..need no special tool, they just screw on. My question is... I did not take note which hose they connect to... when I had to attach the new ones. Which skinny hose the long line/short line go to. OMG... The two skinny hoses on my jeep on hose has 2 nuts( sit right on top of each other then rubber hose attatched to it, the second skinny rubber hose does not have 2 nuts before it. would you happen to know which hose the long/short radiator line connec to? please help

[@SalFettucini]

Hey Martin, any idea if a trail dash 3 is compatible with a 2002 WJ?

[@martinbuilt]

Looks like the trail dash three is only made for 2007 and later Jeeps 2007-2010 3.8L Jeep JK 2011-2018 3.6L Jeep JK 2018-2021 3.6L Jeep JL non-eTorque 2018-2022 2.0L Jeep JL eTorque/non-eTorque 2020-2021 3.6L Gladiator *For 2015-2021 model years, an unlocked PCM will be required, but our PCM Swap is included with the purchase of the device.

[@user-lq1gi9hv7k]

Did you test the temperature difference using the radiator cooler and the trans cooler in series?

[@martinbuilt]

No, I didn't. It would be a higher temperature for sure. It would give the trans a quicker warm up.

[@user-lq1gi9hv7k]

@@martinbuilt what is the brand of your OBDII scan adapter and where can I find one? I'd like to monitor my transmission temperatures. What is the app you used? Did you buy the app or use it for free with ads? I got a scan adapter off eBay but it didn't work, the app could not detect the scan adapter.

[@martinbuilt]

@@user-lq1gi9hv7k This is what I am using to monitor Trans temp and much more. Superchips 42050 TrailDash 2 Programmer w/Mileage Coach Software TrailDash 2 Programmer amzn.to/2xUOv4l This is permanently mounted in the Jeep.

[@merrittmcdowell8675]

What engine are you running

[@nebulousJames12345]

It's hard to see. but was that put right in front of the condensor? It didn't look like you had the condensor in.

[@martinbuilt]

Yes, 1" in front of the condenser.

[@nebulousJames12345]

@@martinbuilt Ah, I was mixed up. I mean to say power steering cooler. It looks like my 2002 wj 4.7 has power steering cooler on the passenger side in front of the condensor. Does this transmisison cooler go in front of that/ or do I need to modify (get longer) hoses in order to put on the driver's side?

[@martinbuilt]

@@nebulousJames12345 On my 04 the power steering cooler is the top portion of the A/C condenser. You may have to move the trans cooler to the other side or in front of the PS cooler.

[@RDJL559]

So you completely bypassed the oil cooler built into the radiator? I thought you only splice into the return line?

[@martinbuilt]

You can just splice into the return.. I just wanted to try and see how it worked by bypassing the radaitor cooler all together. I've been driving it this way now for at least 15,000 miles.

[@drivemecrazyk8897]

what temps do you get in winter, one of my lines are leaking so i was thinking of doing this instead of fixing it, but I live in michigan and it gets cold, do you think it would be ok during winter? love your vids, just recently subscribed!

[@martinbuilt]

drivemecrazy k during the winter time here it probably doesn't quite reach normal operating temperature until you get into stop and go traffic. So most of the time it's like 125 to probably 165. I used to live in Iowa so I know what you're talking about. I would run it through the radiator cooler first then through the auxiliary cooler.

[@kathykoss4231]

@@martinbuilt 9

[@steelerdynasty2007]

@@martinbuilt what would that change from the video? i dont know which one is "in" and which is "out"

[@bujanah]

very nice mod .. i thought it would lower the engine temp but it seem to only effect the trans temp ... the other thing is I read somewhere that maintaining a 215 f would drop valve seat and your engine running 221 did it effect you engine in anyway ?!

[@martinbuilt]

it didn't have any effect on engine temp, I have since replaced the hydraulic cooling fan with an electric and now the engine runs between 180 and 200* with a 180 T-stat. I believe the cause of dropped valve seats is improper purging of air from the cooling system. The air must be removed from the cooling system.

[@bujanah]

@@martinbuilt I'm planning on changing Tstat to 180 and doing the hydra fan solenoid mod maybe tomorrow but i feel that it's not the solution ... as for the hydra fan my research concluded that there is smth wrong in the connection. the fan solenoid is controlled by JTEC with pulse modulated signal that controls the fan speed from 0 to 100% ... if you applied direct 12v to the solenoid it go directly to 100% because of bad connections i believe the signal is lost in the way that is why it won't speed up .. only if the engine temp reaches 220 PCM would apply 12v to the solenoid ... what I'm trying to figure out is how the trick the pcm to put the fan on 100% when it reaches 210 ... I'm thinking of moding the engine temp sensor to report higher temp than it actually is so when it reaches 210 it will read it 220 and trick the pcm to go to full mode on the fan ... sorry for writing too much but i hope you may have some thoughts on this

[@martinbuilt]

@@bujanah you could do that by adding a resistor to the temp sensor just enough to read a higher temp. This would most likely also see a higher temp on the temp gauge.

[@bujanah]

@@martinbuilt hi .. i have added the resistor and it works great no more overheat or creeping to the other side of the temp gauge ... I've added almost 12.6 f degrees so when it hit 208 it will report 221 which will ramp up the fan ... the only issue to notice is that I'm having a rough startup and it almost stall but then it picks up and runs great ... why do you think this is happening?

[@martinbuilt]

@@bujanah that's great that it worked let me know exactly what resistor and how you tied it in. Your symptoms on startup sound like the idle air control valve is faulty or needs to be cleaned.

[@tightcutz3502]

Do u have a video of taking out the radiator

[@martinbuilt]

Matter of fact I was working on one and then realize I was missing some video shots. Went down to pick a part today to reshoot some of it hopefully in the next few days I'll have a video out... I wasn't about to tear my Jeep apart again just to reshoot how to take the radiator and cooling fan out. It is a job.

[@maniacalmonster2293]

Now how much lower would it be if you would have connected it to the original one and had them BOTH operating instead of replacing the original?? Why wouldn't you do that?

[@martinbuilt]

One thing that will do is warm the trans up quicker not that that is a bad thing. The main reason I did it was if the engine is running hot then so is the trans.

[@toku58]

How does your WJ show you the transmission temperature?

[@martinbuilt]

amzn.to/3JjVZTu With this trailed dash 2

[@laragreene8328]

So you can remove it and put things back factory original if you want to?

[@martinbuilt]

yea, other then the mod I made to the header panel

[@JacobEcret]

220 for a trans temp is insane in my opinion, a transmission can run at 150° all day and be just fine

[@martinbuilt]

Yeah I totally agree.

[@sebooher95]

what temp does the BAT stand for next to the intake air temp?

[@martinbuilt]

Battery temp. Don't ask me how it knows what the battery temp is. It would have to be through the ECM some how.

[@sebooher95]

thanks for the fast reply. the only thing i could think of was battery temp but i cant see how thats relevant on a lead acid

[@DanielPace92]

If it's like the XJs, there is a sensor in the bottom of the battery tray that is a temp sensor for the battery, that's how my 00 XJ is. Supposedly it will stop the alternator from charging the battery if it gets too hot, or at least decrease the amps.

[@martinbuilt]

+Daniel Pace. thanks for letting us know and makes perfect sense.

[@sebooher95]

yeah i have noticed a small plunger on a spring under my ZJ battery i wonder if that has anything to do with it

[@genesis14ifi]

HOW REPAIR MY JEEP GRAN CHEROKEE 4.L 6 ON LINE MY JEEO HAVE LOST OF ENERGY BATERY