Thread: Bypassing the in radiator tranny cooler

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  1. #1 Bypassing the in radiator tranny cooler 
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    I am replacing my tranny cooler lines tomorrow and swapping out the stock small tranny cooler and putting in a large 15" cooler and bypassing the in radiator cooler. My question is on the bottom radiator fitting, the part with the tube sticking out. It is loose inside the tank, or so it looks. If Im not running a hose on here, do I need to worry about losing coolant?
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  2. #2 Re: Bypassing the in radiator tranny cooler 
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    If the tube comes from the tranmission part it won't matter.
    04 Dub -- Longarms, JK44, 9" ARB's etc.
    68 Super Wagoneer - Resto Project
    93 ZJ: longarms, 231D, 35's, 44/Hi 9", ARB's, etc. -- Sold
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  3. #3 Re: Bypassing the in radiator tranny cooler 
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    The transmission cooler part of the radiator is completely separate from the coolant. It'll be fine, but I'd cap off the openings to prevent rust.
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  4. #4 Re: Bypassing the in radiator tranny cooler 
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    It turns out mine is leaking from around that brass nut that goes around the line that sticks out the near the bottom. But unfortunately, thats the least of my worries right now.
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  5. #5 Re: Bypassing the in radiator tranny cooler 
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    Why not add the 15" cooler to the 2 existing factory coolers? I have never understood why people do this. There is plenty of room on ZJs so room is no excuse. 3 is better than 1.
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  6. #6 Re: Bypassing the in radiator tranny cooler 
    Senior Member jborushko's Avatar
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    i tore a additional stock tranny cooler out of my parts jeep and plumbed that in line with what was there now thats on the cheap!... also plumbed in a remote tranny filter... ha ha

    screw paying $100 or whatever for another one! course i'll change my tune... but for now on the cheap is for me!
    96 ZJ swapped in 5.2, 242, 14bolt rear, big ugly home brew bumper, 7.5" of lift in the front 9" in the rear, long arms, hummer wheels with 37s... (dont worry front axle is next)

    It should be heavy. Weight is a sign of reliability. If it doesn't work, you can always hit him with it.

    -e-boner
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  7. #7 Re: Bypassing the in radiator tranny cooler 
    Member 96JGCL's Avatar
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    i grabbed an aftermarket cooler, took my factory hard lines out, replaced them with rubber chem resistant hose, and put them right on the aftermarket cooler, totally bypassing the factory in rad one. Works fine for me
    2005 Ford F150 STX 4.6L Auto Daily / Tow Pig
    1996 Jeep GC Laredo 4.0L Auto Mud toy / wrench slut
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  8. #8 Re: Bypassing the in radiator tranny cooler 
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    Yeah, I got mine bypassed a while back. I had to cut off the quick disco portion of the hardlines and attach rubber lines around the rad. The main issue I was having was that the radiator was leaking slightly around the lower fitting on the radiator. But it doesnt really matter, because the transmission went out for good about a mile after the cooler was installed(crack in the case got worse and the tranny was dead), so this facilitated my V8 swap, so the radiator got pulled anyway.

    But now I have a freshly warrantied (1 mile of use) set of cooler hardlines that I dont know what to do with now.
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  9. #9 Re: Bypassing the in radiator tranny cooler 
    Senior Member zj95's Avatar
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    Quote Originally Posted by finn187 View Post
    Why not add the 15" cooler to the 2 existing factory coolers? I have never understood why people do this. There is plenty of room on ZJs so room is no excuse. 3 is better than 1.

    Because a 15" cooler is enough to keep your trans cool, Even here in AZ, and there is no reason to run your transmission fluid into a 210* radiator.

    then you can use your factory external cooler for a power steering cooler.
    95 ZJ/ 5.2 / HD Dana 44 front / 14b rear / 5.5" CLAYTONS / 38'' Grooved TSL's / CLAYTONS belly skid / NP231 w/sye

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  10. #10 Re: Bypassing the in radiator tranny cooler 
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    Mine bypasses the rad. as well. Two reasons, as already mentioned the fluid actually stays cooler not going through the hot rad...and when my torque converter ate inself it left remnants in the cooler part of the rad we couldn't get out.
    04 Dub -- Longarms, JK44, 9" ARB's etc.
    68 Super Wagoneer - Resto Project
    93 ZJ: longarms, 231D, 35's, 44/Hi 9", ARB's, etc. -- Sold
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  11. #11 Re: Bypassing the in radiator tranny cooler 
    Senior Member jborushko's Avatar
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    jsteves.... ? torque converter ate is self? i thought the zj had a sealed torque converter or do you have the AW4 tranny?
    96 ZJ swapped in 5.2, 242, 14bolt rear, big ugly home brew bumper, 7.5" of lift in the front 9" in the rear, long arms, hummer wheels with 37s... (dont worry front axle is next)

    It should be heavy. Weight is a sign of reliability. If it doesn't work, you can always hit him with it.

    -e-boner
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  12. #12 Re: Bypassing the in radiator tranny cooler 
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    All I know is I had a pan full of brass shavings and the tranny no go. I assumed converter was the cause.
    04 Dub -- Longarms, JK44, 9" ARB's etc.
    68 Super Wagoneer - Resto Project
    93 ZJ: longarms, 231D, 35's, 44/Hi 9", ARB's, etc. -- Sold
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  13. #13 Re: Bypassing the in radiator tranny cooler 
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    Quote Originally Posted by finn187 View Post
    Why not add the 15" cooler to the 2 existing factory coolers? I have never understood why people do this. There is plenty of room on ZJs so room is no excuse. 3 is better than 1.
    Are you not familiar with the fact that too many or too large of a cooler will simply block airflow to the radiator?
    96 4.0 ZJ, 4.5in RE coils with Teraflex arms, Yukon gears, ARB front bumper, 33x12.50 M/TR's, homemade OBA setup....

    97 with stuff....
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  14. #14 Re: Bypassing the in radiator tranny cooler 
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    Quote Originally Posted by black_zj View Post
    Are you not familiar with the fact that too many or too large of a cooler will simply block airflow to the radiator?
    Not true. Adding a 15" cooler to the small factory will not cause problems. If it does you have other issues.
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  15. #15 Re: Bypassing the in radiator tranny cooler 
    Senior Member jborushko's Avatar
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    its amazing how well your fan will pull air in if you tear out the A/C condenser... i hit the throttle by hand one time and sucked a [empty] qt. of oil off my bumper and it stuck to the radiator... i laughed
    96 ZJ swapped in 5.2, 242, 14bolt rear, big ugly home brew bumper, 7.5" of lift in the front 9" in the rear, long arms, hummer wheels with 37s... (dont worry front axle is next)

    It should be heavy. Weight is a sign of reliability. If it doesn't work, you can always hit him with it.

    -e-boner
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  16. #16 Re: Bypassing the in radiator tranny cooler 
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    Quote Originally Posted by zj95 View Post
    Because a 15" cooler is enough to keep your trans cool, Even here in AZ, and there is no reason to run your transmission fluid into a 210* radiator.

    then you can use your factory external cooler for a power steering cooler.
    Actually there is a reason to run tranny fluid through a warm rad...the tranny has an optimal operating temp that's only a few deg cooler than the motors prime operating temp.
    If you live in a climate that gets below 40* for a few months or more don't bypass your rad "cooler".
    97 grand cherokee ltd, 5.2, white, many mods of debatable value.
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  17. #17 Re: Bypassing the in radiator tranny cooler 
    Junior Member cadmaro's Avatar
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    Auxiliary coolers are just that, AUXILIARY coolers. Water cools significantly better (faster) than air always, period. The transmission fluid comes directly from the transmission at a much higher temperature than the water in your radiator and is cooled to the water temperature fast. Then it goes to the auxiliary cooler to be cooled far below the water temperature. If you don't need a cooler in your radiator why do the auto manufacturers spend all that money putting it there? If you wanted to cool a red hot piece of steel fast would you stick it in water or air? For the best cooling you need both water and air cooling for the transmission to be cooler than the motor.
    Last edited by cadmaro; 06-30-2010 at 01:15 PM.
    Kevin R.
    94 ZJ i-6 , 5-speed , 4.5" lift with IROR and BDS parts, 33x12.50 thornturds on soft 8s
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  18. #18 Re: Bypassing the in radiator tranny cooler 
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    Will bypassing the Radiator-Trans cooler help my engine overheating issues? That is the main reason I was considering bypassing, I run hot with the 4.7L and am looking for ways to keep her cool.
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  19. #19 Re: Bypassing the in radiator tranny cooler 
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    I know this is an old thread but I just moved to Tuesday,AZ and my Jeep already runs hot when the AC is on when I visited here last summer.
    I want to pull the trigger on a transmission cooler and run it straight to trans but I'm unsure of what model to get.
    I've got a 94 zj Laredo 4wd 4.0 any help is appreciated I came from jeep forum.com but I haven't gotten any feedback on which cooler to purchase that is capable of bypass.
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  20. #20 Re: Bypassing the in radiator tranny cooler 
    Senior Member Ken L's Avatar
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    I went the route you're considering. I put a big transmission cooler in front of the radiator, and it proved not to be the brightest move. It blocks too much air flow, and the radiator couldn't keep up. I moved on to this cooler https://www.amazon.com/Derale-13740-...ion+cooler+fan and it's made a world of difference with overall cooling. Especially if your Jeep is a daily driver, I wouldn't put anything more in front of the radiator.

    I had to relocate a bunch of stuff under the hood to make room, but it wasn't too difficult.

    Hope this helps.
    Ken L
    '96 ZJ with stuff
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  21. #21 Re: Bypassing the in radiator tranny cooler 
    Senior Member Grand Slam West Planner K2's Avatar
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    I used a smaller one, 12x8" maybe, and bypassed the radiator. I didn't have any cooling problems until I installed a stroker motor.
    02 WJ, Lift, dents, noise and smoke.
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  22. #22 Re: Bypassing the in radiator tranny cooler 
    Senior Member DJJordache's Avatar
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    Ken any pics of the location? I'm about to do just this but would prefer to lighten the load on the radiator if possible....
    I'm running a transmission oil filter on the output of hte transmission BEFORE it goes into the coolers then back to the tranny right now.
    93' ZJ 4.7L STROKER, Clayton LONGARMS, 4wd conversion, 231 SYE, HPD30, 8.8, BFG 35's, 2000 manifold & injectors, Hesco fpr, Port & polish, LS1 valves, WJ Steering/brakes, KOR SliderZ & steering box brace, Clayton TB bracket and my custom trackbar, Crane ignition, B&M cooler, Tom Woods, etc....
    Quote Originally Posted by Krash80 View Post
    We're all insane here...
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  23. #23 Re: Bypassing the in radiator tranny cooler 
    Senior Member Ken L's Avatar
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    Quote Originally Posted by DJJordache View Post
    Ken any pics of the location? I'm about to do just this but would prefer to lighten the load on the radiator if possible....
    I'm running a transmission oil filter on the output of hte transmission BEFORE it goes into the coolers then back to the tranny right now.
    I'll try to get a pic posted in the next few days. I haven't picked another hosting site since Photobucket shit the bed, but I do need to do that.
    Ken L
    '96 ZJ with stuff
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