If u bypass the OEM rad tranny cooler, u would be well advised to install an aftermarket temp gauge to monitor tranny fluid temp. The temp gauge sending unit should be mounted in the hot fluid exit line.....not the cooled fluid return line.

 

I just can't imagine that coolant change happening overnight. I would guess transmission fluid mixed with coolant would be more of a white or gray color than anything.
For reference google " dex cool death" & you get


The fix: expensive or Craigslist it.

 

I agree, coolant doesn't NORMALLY change overnight.

I've seen some of those DexCool posts on the Interweb and have been puzzled. Had 2 GM vehicles, both 6-7 years old and 100K miles on original DexCool. When I drained both cooling systems summer of '13, what filled the drain pan was virtually as clean as new. Zero, zip, nada sediment/crud. Didn't flush either vehicle because there was no crud around the t-stats or in the rad hose nipples.

Took the 3 jugs of Prestone Extended Life back to the parts store and exchanged them for 3 jugs of DexCool. DexCool works pretty good in my experience but I guess any coolant can turn crappy when cooling systems r neglected, not maintained or something internally in the cooling system goes wrong.

 

The photos look like rust not ATF, it should be easy to ID the difference being up close and personal if it's oily stuff or not. Why it would suddenly be rusty? Maybe a grounding/electrical issue causing electrolysis? If there's nothing obviously wrong other than the rust I'd say flush it out and monitor it.

 

That's definitely rust.

 

^ this is not a picture or the vehicle with the issue

 

Why oh why?
the oem in-radiator trans cooler is a joke in the first place. In our rhd setup, the translines are even entering the hot side of the radiator to make things even worse. A good aux trans cooler will do fine. Everybody gets all hyper with putting trans temp gauges in, which is useless since you cant do anything with that. There is a reason why it doesn't come with one from factory and that is that not everything needs to be monitored. The same reason why there is not an oil temp gauge. The AW4 is a strong trans and can stand some heat. Again, a good aux cooler will do, and just forget about adding another unnecessary gauge to frantically watch.....unless you like that kinda stuff.

 

Something tells me in the early design phase Jeep engineers tested/evaluated, under numerous/various driving conditions, how the well the OEM tranny set-up performed, including tolerable fluid temp. They didn't just slap something in there and call it a day without any testing. One of the devices used in testing was a tranny fluid temp gauge and from the results they obtained (fluid temps), they determined the set-up they designed was adequate under most driving conditions. If it wasn't adequate, including tolerable fluid temps, then back to the design drawing board. Since the engineers used a tranny fluid temp gauge to determine all is good, they determined that a factory tranny fluid temp gauge would not be necessary.

If u change the OEM tested design, how r u going to tell for sure if the altered design change will give tolerable fluid temps, at least as good as those that have been proven by testing under all driving conditions? When u stray from the factory set-up, u r guessing/taking a chance that the at the alternate set-up performs as well as OEM, unless u test the alternate set-up. My thinking is, u need a temp gauge to verify and not guess at fluid temps when change OEM. That's the way the Jeep engineers did it.....using a temp gauge during testing, no?.

 

You regard the In-rad trans cooler far too important. Your jeep engineers decided to let the transcooler lines enter and exit on the hot side of the radiator in the rhd. I dare to say that actually adds to the increase of temps instead of cooling things. You probably regard these engineers too important as well

The aux trans cooler that came on my 97 Sport is horribly small, but does a better job than the in-rad cooler with translines on the 'wrong' side. I'm no at all against testing temps, but its not necessary as a permanent thing. It will only give people another gauge to frantically worry about and than come with questions how to lower the trans temp. Fresh and maintained ATF, correct level and a good aux trans cooler ( and if you see the tiny size they came with, almost any aftermarket aux cooler will do a good or better job), and you will be fine.

 

JMHO, I would at least hit the pan with an IR temp gauge under different driving conditions to make sure you've improved things and not made them worse. Should always verify mods, not just assume.
From there a perm. gauge is your choice.

 

Sure, but thats in an ideal world. I'm all for verifying things, thats not the point...but I dare to say not even 10% of those who fit an aftermarket aux trans cooler, will put the effort in to do so.....

And rerouting the OEM setup being such a worry? Just look at the differences between the LHD and the RHD setup with or without an aux trans cooler and you will see that even with a lot of abuse, and despite some folks at engineering HQ decided to take an early mark on friday, the AW4 manages to function fine. I say, once again, its nice to know , but from there on will make little difference. Not everything in the XJ needs to be scrutinised , IMHO.

In the end, please do what you feel most comfortable with.
Shall we move on?

 

It's very odd that they'd change the cooler location for RHD; you're sure it's in the hot side of the rad., the end with the upper rad hose? Very curious.
A gauge generally isn't needed on a stock set-up being used within it's design parameters, once things are changed I would suggest at least a temporary gauge while it's driven in all the conditions it'll be driven in.
Another issue with ridding the radiator mounted cooler and going all air is that the fluid may run too cold, not good. It's also another thing blocking airflow to the already challenged radiator in many XJs.

 

well, in my RHD it is that way, so yes, I'm sure...

 

R we talking 2 different things here? My definition of "auxiliary" is a second cooler that is in addition too the OEM or primary cooler. We have a auxiliary (secondary) cooler mounted inline with and after the OEM "primary" cooler. No temp gauge or verification needed as we have not replaced the OEM cooler but rather added to it's efficiency.

If u eliminate the OEM cooler and change it's location with an aftermarket replacement cooler (still only one cooler), might want to verify that the alteration to the OEM set-up works at least as well as the Factory OEM set-up. How u gonna do that without monitoring fluid temp. Why do folks change out idiot light instrument panels for a instrument panel with all those unnecessary gauges? I was only making a suggestion since "cooling" in one form or another seems to be a "hot" topic almost year round.

 

Dont have my FSM here, but here (below) a pic of the LHD setup (btw, there is already at least one thread on this, also with this pic)

And here a link for a pic of the RHD setup. Not the best of pics, but just to illustrate.
http://www.factorychryslerparts.com/...ey_model=15525