Kymasabe

My apologies for posting this question here but owning an '04 WJ with a 4.0 motor and my '99 XJ with a 4.0 motor as well, I've found that the mechanical expertise and advice here in the XJ forum far exceeds that of the WJ forum. I'm not gettin answers on the WJ side, so thought I'd try the same question here, so here goes:
My wifes 04 WJ has 4.0 liter and 2WD 42re transmission. No trans cooler in the radiator, is running aftermarket cooler in the grill only, looks around 11x7 cheap tube and fin cooler. The hoses are starting to look rough/cracked so I need to at least replaced the cooler lines to the cooler, but was thinking of replacing the cooler while I was there with a more efficient staked plate cooler of at least the same size, and possibly larger. But, if I put an 11x11x.75 cooler in there, will it block so much airflow that I risk the engine running hotter?

Next question: Right now my cooler is ziptied to the condenser and radiator with those cheesy zip thingies that come with the coolers. I want to mount the new cooler to the radiator support in front of the condensor but, I may end up an inch or more in front of the condensor. Will a large gap between the trans cooler and the condensor cause a problem? I'm afraid if the trans cooler is too far forward, the fan won't draw air thru it and it won't cool properly.
Your thoughts ??
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s346k

my experience. i installed a large aftermarket trans cooler. it covered ~60% of my radiator. i did not notice any change in coolant temp, but the transmission definitely did not like it. it cooled far too well. i omitted the radiator from the trans cooling. i eventually replumbed everything back to stock. 240k miles and 0 issues. i made a 1,014 mile trip this week including a drive through the smoky mountains (both ways) on 441.

sneeze357

Just like everything else, you want some heat in your transmission, just not too much. It has a certain ideal operating temperature. If you have too big of a cooler, you can over cool it...especially if it's cold outside and you're not very heavily loaded. Some trans coolers come with a thermostatic bypass for this, so they don't work when the fluid is cold.

kbeam418

You must run the fluid through the radiator or the fluid will be too cool and will not shift right plus it will damage the transmission. No the engine shouldn't run any hotter, the fan may come on more often but it shouldn't overheat assuming the cooling system is good. You want the trans fluid around 180 if I remember correctly. Get a cooler with a thermostat to avoid overcooling.

jeep94Norway

If you are going to buy a new cooler to the transmission don't forget to buy a oil thermostat to it. cost around 60-80 $. take the 160 Fahrenheit . this will help you get the transmission up to temperature faster. how it works, is it bypass the oil from the cooler before it reaches 160 Fahrenheit. the stock setup for the transmission is not good but its better then nothing.

with a oil thermostat of 160 fahrenheit your transmission will run around 75+ degree celcius on the outline of the transmission.
make a good bracket for the cooler don't use ziptie.