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Automatic transmission cooling lines

BobK

TJ Enthusiast
Supporting Member
Apr 11, 2019
131
Parker, TX
Because I am on a mission to replace all of the rubber bushings, hoses, and belts on my 2003 TJ, I'm wondering about the transmission cooling lines. I see that they are partially rubber with some steel lines in certain areas. I have been unable to find a complete replacement set of tranny cooling lines. But I am finding a bunch of fittings to replace all of the existing fittings with attachment to rubber hoses. Is this a common replacement strategy? Will ordinary hose clamps hold all the pressure lines for the transmission fluid?

Any thoughts, cautions, or alternatives will be welcomed.

Thanks
Bob
 

dudehitt

TJ Enthusiast
Feb 5, 2019
275
Phoenix
I waited until someone with more auti trans vehicle experience chimed in, but in industrial hydraulics coolers are always on the low pressure side. After all the heat generating tiny orifices and things you can't see.
 
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Flivver250

TJ Enthusiast
Supporting Member
Jun 3, 2018
583
Dubai/Florida
When I used to work on vehicles decades ago, I was in a very rusty area. Tranny lines used to rot out and we'd replace them with neoprene hose. No issues at all. Shops always had spools of fuel hose and the like.
 
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BobK

BobK

TJ Enthusiast
Supporting Member
Apr 11, 2019
131
Parker, TX
OP
BobK

BobK

TJ Enthusiast
Supporting Member
Apr 11, 2019
131
Parker, TX
There's not a lot of pressure in the coolant lines. Simple constant tension clamps like the factory used on some ATF lines or barbed hose fittings are enough.
Thanks Jerry, I was unsure about the pressure given the steel (or aluminum) lines used. Seems like it would be much easier to cut and route rubber hosing than the metal ones.

Bob
 

Jerry Bransford

TJ Guru
Supporting Member
Nov 9, 2015
10,625
Escondido California
Maybe I spent more than I needed to on my transmission cooler's hose but it's rated for higher temps than standard neoprene hose is. The upper temperature range for standard neoprene is only 220 degrees. Above where you want the transmission's ATF temp but not above it in all possible situations. The size needed is 3/8" I.D.
 
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BobK

BobK

TJ Enthusiast
Supporting Member
Apr 11, 2019
131
Parker, TX
Maybe I spent more than I needed to on my transmission cooler's hose but it's rated for higher temps than standard neoprene hose is. The upper temperature range for standard neoprene is only 220 degrees. Above where you want the transmission's ATF temp but not above it in all possible situations. The size needed is 3/8" I.D.
Have you replaced all the metal lines with the neoprene hose? Is the standard dimension 3/8 ID?

I read a thread of yours on a cooler setup. Do you still recommend the same one? Is the fan necessary or can I go with just a cooler, since I'm not expecting heavy duty off-road and/or trailering?
 

pagrey

TJ Enthusiast
Apr 10, 2018
490
Los Angeles, CA, USA
Don't use neoprene. It is not rated even close to the temp and pressure required for those hoses. Grainger says that hose is rated to about 10psi at 75F which is nowhere near what you need. Just use transmission cooler or oil cooler hose. It's rated SAE J1019 and sold everywhere. Gates, Continental and Hayes all make it. You want the black rubber like hose that has white cords visible when you cut it.

You should get a transmission temperature gauge before you get a cooler. There is no need to put a cooler on Jeeps that aren't running large tires or pulling trailers even in warm climates. You already have an oil to water cooler which is fine for most people.
 

Thunderhead

TJ Addict
Supporting Member
Jan 19, 2018
1,026
Orland, CA, United States
You should get a transmission temperature gauge before you get a cooler. There is no need to put a cooler on Jeeps that aren't running large tires or pulling trailers even in warm climates. You already have an oil to water cooler which is fine for most people.
Its an Auto, get the cooler.
I have a passive B&M cooler. I'm not in JV on rocks but I am in Nor Cal with 110 degree temp.
 
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mrblaine

TJ Expert
Supporting Member
Nov 20, 2015
4,794
Quail Valley, CA
Its an Auto, get the cooler.
I have a passive B&M cooler. I'm not in JV on rocks but I am in Nor Cal with 110 degree temp.
Cooler or not, get a gauge in there first. Once you know what the temps are, then you can decide on the cooler. I don't run them on most stockers, I always run them with larger tires even if the gearing is correct. I run nothing without a gauge because I don't want to guess at the temps and I want to know if the cooler is doing its job.
 
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BobK

BobK

TJ Enthusiast
Supporting Member
Apr 11, 2019
131
Parker, TX
For those of you that run a transmission cooler without the fan. Have you installed it in front of the radiator but behind the grill? How do you mount it? Doesn't it interfere with the cooling of the radiator?
 
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mrblaine

TJ Expert
Supporting Member
Nov 20, 2015
4,794
Quail Valley, CA
For those of you that run a transmission cooler without the fan. Have you installed it in front of the radiator but behind the grill? How do you mount it? Doesn't it interfere with the cooling of the radiator?
I always install in that spot if possible. I use a too expensive cooler, but that is where it sits and it causes no other issues.
 
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hunter1

New Member
Jan 17, 2019
15
Lafayette, LA
I've been thinking about a front cooler too. If I mount a gauge as well, where does the sender mount? I found a YT vid that talks about install on the trans pan, but a whole lot of trouble. Does my 2002 auto have a OEM pickup point somewhere?
 
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BobK

BobK

TJ Enthusiast
Supporting Member
Apr 11, 2019
131
Parker, TX
I just ordered the B&M cooler. Does anyone know what fittings I need to attach new rubber hoses to the transmission, since I am going to remove the metal tubing with rubber hoses. It would appear that I need two fittings that screw in or attach to the tranny.
 
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