Trans. cooler

Yes you can bypass the factory cooler in the radiator. It probably won't have a noticeable affect on water temps unless your trans is running way hot and if it was then you would have a far bigger problem than what a auxiliary transmission cooler could cure. I added one because my transmission would over heat on the highway if I pushed the transmission too hard by downshifting trying to go too fast. The trans fluid would get so hot it would expand so much it would come out the dip stick tube and drip on the exhaust and leave a trail of white smoke behind the Jeep. Since putting the trans cooler on and bypassing the radiator the trans runs much cooler and I never have the problem with it overheating that bad anymore. I also installed a trans temp gauge to keep a close eye on it.

ZJ trans coolers fit perfectly behind the front crossmember

Anyone stuck the probe in the drain plug? Instead of putting in a t?

The usual way is to keep the radiator heat exchanger and add the second cooler in the return line. The reason for this is that the radiator not only cools the fluid when it's hot, but warms it when it's cold. The factory heavy duty tow package does it this way.

Would the probe get sheared off by a strategically placed rock in just the wrong spot?

I don't use the radiator loop. I've had it that way for 30K miles with no issues. Just tranny to cooler (11x11") and back to tranny. Freezing temps are few and far between here.

If you live in an area that sees severe freezing temp then I would recommend keeping the fluid going through the radiator as well the aux cooler. But if you live in an area where at best you may see some flurries to an inch or two of snow during the winter then you should be just fine running straight through the aux cooler and bypassing the radiator all together. If you want you can always rig up a valving system where you can switch back and forth between going through the radiator or bypassing it. Thats just an option if you want to go that far and willing to put in the extra work.

I'm all for modifications for the sake of modifications, but one question:
What is the problem you are having that you are trying to solve?
Once we know that, we can give better advice.
If you can't answer the question, you might put your attention elsewhere on the jeep.

bonesxj said:

I want to put a bigger tranny cooler on my XJ. The stock one runs through the radiator, can I just bypass that part of the system and add the aftermarket one. I was also thinking this would help on keeping the water temp. down some..

Click to expand...

As the others have mentioned .... Yes

Best "bang for buck" setup will be a 10"x12" stacked plate cooler mounted behind the grille/in front of the rad ... in line with clutchfan.

Other locations and oil cooler fans etc ... may be more suitable ... depending on your driving requirements.

Anything you can do to make the radiator function to the best of its ability is a good thing ... and that includes bypassing the heat exchanger.

If your weather is such that the heat exchanger is actually a benefit for the gearbox ... its effect on the radiator will be negligible.

I live where in the summer the temps. can be as high as 90 to 100 degrees and the winter we can have 6 to 8 feet of snow on the ground and temps. as low as 0 degrees. In the winter the average temp. is 40...All my driving is up or down hills very little flat road around here..I'am also running 33'' with stock gears for now hoping to get new gears this summer..