XJ Transmission Oil Coolers

[Deezelweazel]

Ok, and you do know that tranny fluid also needs to have an operating temperature to avoid unnessecary wear?
The inline tranny cooler is very effective. And according to bernoullis first heat law most people obviously do not understand how it works.
Heat is aleays transfered from hot to cold never vice versa.
That means tranny fluid will never get heated up by coolant except during warm-up which is intended in this way to gurantee a quick operating temperature of the fluid.
Temps lower than 80°C cause increased wear inside the tranny.
so an aux cooler has to be adjusted to the performance line.
Bigger is not always better.

[carvesdodo]

Originally Posted by Deezelweazel

Ok, and you do know that tranny fluid also needs to have an operating temperature to avoid unnessecary wear?

ummm yep ... and even tho I read all chrysler FSM temperature info with just a hint of sceptism ...

The FSM states 50'c - 80'c for the AW4 ...

Now since the AW4 in the XJ is known to run "hot" compared to other autos and even the AW4 in other brand vehicles ... I'm quite prepared to accept the "low" factory specs & lower ... as a nescessity, for a sump temp ... when reading similiar info to this --> http://www.digi-panel.com/trannyoil.htm

Of course there is no indication in the FSM whether that is a sump temp, or an after torque converter temp ... or an internal operating temp ....... but its probably safe to presume its the sump temp ... given expected higher temps of the other two.

Originally Posted by Deezelweazel

The inline tranny cooler is very effective. And according to bernoullis first heat law most people obviously do not understand how it works.
Heat is aleays transfered from hot to cold never vice versa.

Effective - when the heat exchanger is in the correct side of the radiator and has cooled radiator liquid, to transfer heat to ... and the engine cooling system is adequate enough in all driving conditions, to not be affected by the heat transfer.

The fitment of the little aux cooler, to RHD export 4.0l models - with the heat exchanger in the radiator hot side ... is obviously an attempt to provide the same cooling result, as LHD, snowbound XJs, radiator cold side, in-tank heat exchangers - which dont have an aux cooler fitted as standard.

According to chrysler specs ... the aux cooler is required for heavy duty use of the gearbox ... therefore IMHO .... the factory aux cooler, is a nescessity for Aust. versions - but is not a generous gift from chrysler coz they thought we all towed stuff ...

It needs to be upgraded for heavy duty use ... and perhaps even just to make up for our higher average, ambient temps - which dont have as big a windchill factor on radiators/coolers, as what northern hemisphere average, ambient temps do.

Originally Posted by Deezelweazel

That means tranny fluid will never get heated up by coolant except during warm-up which is intended in this way to gurantee a quick operating temperature of the fluid.
Temps lower than 80°C cause increased wear inside the tranny.
so an aux cooler has to be adjusted to the performance line.
Bigger is not always better.

Again ... the heat exchanger needs to located correctly for the intended process to function correctly.

Agree with adjusting the cooler to meet operational requirements ... Thats the same as the requirement to tickle the coolant system depending on operation of the vehicle ... and its operating area.

Mind you ... Its that fixation wth a single "best" temp - that is the downfall of the 4.0l cooling system.

Its rather amazing that a vehicle manufacturer thinks that it can pluck a single temp out of ... of ... of .... somewhere .... and make it a target/goal temp .... When all the components / factors that facilitate that temp are variable ...e.g.

Ambient temp windchill factors,
Ambient reflected ground temps,
Coolant mix pecentages,
Radiator core qty & construction,
Driving styles and vehicle use,
Engine loads,
Performance of aged components,
Performance of different brand new components,
Faulty new components,
Maintenance schedules
Fuel type availability.

Much better IMHO to have a system that fluctuates within acceptable limits under the various loads - rather than an expensive, high maintenance system where 100% efficiency of all the variable components/factors is required.

Perhaps tho ... chrysler actually expected everybody who bought an XJ, to only buy genuine parts and liquids whilst having scheduled dealership services done ....


Hopefully everyones input and feedback, in this thread will provide a "most suitable" oil cooler setup for our conditions, at some point in the future.

For those of us working the gearbox hard in the warmer areas of Oz .... and until a known standard is worked out .... I think that initially, bigger is better ..... as a bypass line in parallel with the cooler, is easy done to combat overcooling, if needed ...

As far as a large oil cooler obstructing the radiator airflow goes ... yes, it will ... but I've had enough junk in front of my radiators to show its not that big an issue ... even with factory radiators.
Perhaps tho ........ it is a more critical issue with the TD2.5l.

Fabio has the right approach ..... compromises in some areas need to be accepted - to achieve a balanced, overall improvement.

[Deezelweazel]

I do accept all those thoughts- but why are all tranny coolers located in the front of the radiator?
Heck, there are dozens of better places.
I do agree that the factory tranny cooler is a joke, and I have read the tranny cooler thread very closely.
Engineers do nothing without a reason and the tranny cooler fitment is there for a reason. It simply has bernoullis heat transfer in mind.

I do agree that a huge cooler can be a beneficial aid.
But get it away fom the radiator front. I friend of mine has a huge cooler in front of the radiator- his tranny temps are ok- but coolant raises up to the sky.
I'm sorry to say that- but what an idiot!
I told him to use a fan- what is he going to do? He uses a PC fan with an output of 3(!) watt!
I feel like I would take crazy pills!
3 (three)freaking powerful watts- that's not a fan!!!
Use a motorcycle fan with 100watts! It will suck your hand through the fan!
But you can place the radiator whereever you want to and provide controlled tranny temps with a temperature switch or an in cab override.
Yes, a motorcycle fan is expensive. So is a new tranny!

Manufactures calculate with a 1/8 cent so they choose the cheapest solution possible- don't go this way!

[junglejuice]

Too many times foreign manufacturers send their wares here to Australia with their "experts" saying that if it works in norther Europe then it will work here.... BULL!!!

I used to work in the backup power generation industry and when we asked our European suppliers for "tropic" rated generators for installations in North Queensland and Northern Territory the reply we got back was "Australia is not in the tropics", obviously maps are scarce in some places....
As for things blocking the radiator such as lights etc, they are mandatory in night driving here due to less than adaquate headlight systems fitted to the Xj and the fact that in front of the radiator is the ONLY legal place to fit aux lighting, and besides after one decent drive the radiator is blocked up with bugs anyway.....
The other issue is that in rural parts here the air temps can be 1/3 to 1/2 as high again of some European and North American cities and that can be for 6-8 months of the year and for a vehicle that was really aimed at North American snow areas anything to bring temps down has to be a good thing.
I fitted a reasonably large alloy cooler in series with the standard fluid lines and after a long drive in winter (26-28 degrees celcius) that aux cooler was pretty hot and that was mounted in the lower portion of the bullbar with lots of free air flow.
The other thing that a lot of people from Europe or the US don't realise is that we can drive 1000's of kms and only see a couple of small towns so these engines and trannies are often under much higher and longer loads than our norther hemisphere cousins....

[Deezelweazel]

I do realize that temperature is higher than in europe. But do have in mind that seasonal duration is not an issue.
America has a lot of high heat zones too. (eg.: Arizona, Texas, New Mexico...)
and I remember the heat of Phoenix, Arizona very well. 40° to 50° in the shadow...

I know about the heat transfer problems very well. been often in Otera Mesa, New Mexico, a military desert test ground. The funny thing is semis, watercooled or aircooled worked very well there.
That brings me to the conclusion(again) it must be an insufficient coolant system in Jeeps or other trucks. So it is a money related issue.

When do you need your aux lighting? daylight or night? Are the temperatures comparable or do you have a significantly drop during the night?
It is a fact that obstruction due to aux lightning is significantly high.
So if you need an aux lightning system it has to be designed as a quick release system. Quick(!) removable during daylight.



Do not try to tell me it is impossible.
It is the look and the style most people go for!
The try to impress with that rugged offroad aux lightning style.
( I do like it too, but it is simply not possible with the heat issues.)

I do also understand the need for bull bars. just watch tv,they are visible every in every australian road movie.

I do also know that as an example VW, carry alot of high heat solutions like bigger radiators, reinforced fans, lower operating temperature switches.( so called tropical reinforcement)
When I go through the chrysler replacement part catalog I don't find such items. That brings me to the thought- not necessary or no thoughts about them.
Obviously they know about the problems, because they mentioned the radiator obstruction in the factory manual again and again!

So a solution with quick release pins and a quick electric disconnect seems to be an solution- not taking longer than 30 seconds to install if needed.
I'm pretty sure, that not every distance is a long range distance drive.



Sump temperatures are always lower than internal or in the converter.
Just compare engine oil temps. As high as 400°C below the pistons and around 100°C in the sump- so expect much higher temperatures inside the tranny- while it is not an internal combustion engine.
Preventive maintenance does play an important role here. As an example:
The military does change certain fluids on a daily(!) basis after hard use. Did you have done something like that ever in the past?
When did you replace fluids before you hit an offroad event the last time? This does also belong to prepping.
An oil change before a long ride does not hurt- even if it is not due. But it expands heat carrier abilities and avoids heat stress and stress related failure. The small things do sum up!
another example: an agriculture truck has up to several hundred liter of tranny fluid to work relaible all day long.
Compare that with the small amount of tranny fluid in the Jeep and its heat carrier abilities.

[carvesdodo]

Originally Posted by Deezelweazel

I do accept all those thoughts- but why are all tranny coolers located in the front of the radiator?
Heck, there are dozens of better places.
I do agree that the factory tranny cooler is a joke, and I have read the tranny cooler thread very closely.
Engineers do nothing without a reason and the tranny cooler fitment is there for a reason. It simply has bernoullis heat transfer in mind.

Heya Deezelweazel

Am guessing that fitting the tranny cooler in a better location - would mean a higher production cost, either for proper vents and ducting ... or a fan for the cooler.

In either case, that would mean factoring the oil cooler in as a nescessity during design ... instead of just slapping it in front of the radiator, as a cheap option to keep a small percentage of hot climate customers / small trailer towers happy.

The auto JKs are going through the same process at the moment ... Shame us AW4 XJ drivers werent more aware of the inefficiency/ineffectiveness of the system while the XJ was still current ..... might have got free oil coolers like the JKers are ...

Whats also forgotten over here is that vehicles the size of an XJ, are not the preferred choice of towing vehicle in the U.S.A., for anything much bigger than a small 2x1.5 metre box trailer or jet ski ... and chrysler ... or any other brand, is NOT going to over design the vehicles ... just in case a couple of people want to push them past the towing limits.

Thats called, voiding warranty by improper use .... or something

Whilst we in Aust may may regularly hook up horse floats / caravans or 5m car trailers to an XJ .... and I do ...

........... Some one in the U.S. is much more likely to go and buy a real tow vehicle such as a ford or chev V8 light truck.

Originally Posted by Deezelweazel

I do agree that a huge cooler can be a beneficial aid.
But get it away fom the radiator front. I friend of mine has a huge cooler in front of the radiator- his tranny temps are ok- but coolant raises up to the sky.

Appreciate the the concern about airflow obstruction ... It definitely needs to be factored in.

I have been running a roo bar, 2 x 200mm driving lights, and a couple of different size coolers over the last 6mnths ... and I've recorded no noticeable ill effects ... but ... to be fair - all cooling components are only 6mnths old to date ... and the fitted radiator does have about a 10%+ efficiency increase over the std factory radiator.

Never had any real issues previously either but I used to watch the temp gauge a lot more often .... Now I just enjoy the view ... but I also have your regular maintenance of cooling system attitude.

Others' results will be different of course, depending on brand of - and condition of, their cooling components.

In fact I've just cleaned and am about to refit the gauze over the grille to keep the locusts out ...
Its bit of a, damned if you do / damned if you dont, situation .... coz even tho the gauze blocks airflow .... so does a heap of grasshopper gutz jammed in cooling fins, after a 4.5hr return drive to the "local" macdonalds hamburger joint ....

And the gauze is a lot easier to clean on the side of the road, than the radiator. .... Theres that "compromise" factor again ... in relation to driving conditions .....

Cute ... arent they ...

Originally Posted by Deezelweazel

I told him to use a fan- what is he going to do? He uses a PC fan with an output of 3(!) watt!

baaahaaahaaa ...... A while back .... I was successfully lowering underbonnet temps with a couple of large, "heavyduty" computer squirrel cage blowers ... until they melted ...

Originally Posted by Deezelweazel

Manufactures calculate with a 1/8 cent so they choose the cheapest solution possible- don't go this way!

Yes thats the underlying problem with virtually any brand vehicle since the late 70's ... gone is production pride ... Its been replaced with just the cash grab at point of sale.

Originally Posted by junglejuice

Too many times foreign manufacturers send their wares here to Australia with their "experts" saying that if it works in norther Europe then it will work here.... BULL!!! ..... / ....

Thanks for climate support junglejuice ......

And Aust is a "hot ambient climate zone" according to chrysler ... As they mention temps of approx 30'c ... as hot ambient in TSB's.

They also just happen to mention in the FSM that hot ambient temps will cause overheating .....

[Deezelweazel]

Impressive, I guess the "clutter" in the first picture is a swarm of grashoppers?

We, the thankfully customers, have to deal with problems the factory does not care about.
I had to learn the ropes with high heat conditions in VW's that were not build for a 50% higher engine performance output.
A general rule of the thumb is: Do not even try to cut the corners. Design it better than factory.(which can be difficult- as a non engineer) So it isvery often trial and error very.
Steal as much improvement thoughts as possible and transfer them all -if you want durability.

I know that butterflies and grashoppers are a problem in australia, and that the net is a common solution.

Oh my god, I do not act as the almighty offroad god I simply want to show different ways to avoid major problems.
Even the undercarriage does offer a lot of space for hidden coolers. They are used also in mil. trucks with a stone guard and do work.

Coolers can be hidden in sheet metal vented with those shark styled vents like those upper class vehicles( porsche did with great success in the Porsche 944 turbo.) Possibilities are endless. I want to attract your attention away from common procedures and to start thinking.

I watch the constant fight against effects- no one fights the causes.
It does not matter where the Jeeper drives.
Australia, USA , Europe- they all behave in the same pattern.
Coolant flushes, coolant additives, added coolers- but no one replaces radiators to increase efficiency. They cut the corners to avoid to spend money.
Of course it is no fun to dump money in coolant repair and a decent set of new BFG mudders does indeed look better than a new radiator.

I also now that there are some people driving the Jeep with a tight wallet. Sorry, absolute wrong vehicle...