XJ Transmission Oil Coolers
 

This thread includes a thread started by chrisXJ which we had merged to keep similiar info together and save some search time.

In addition to the info posted in this thread .... there is also a collection of threadlinks a few posts further down.



As there is lots of thoughts on whys, why nots, sizes, line routing, bypassing stuff, cooler before heater, cooler after heater etc etc .....

How about a collection of info in the one thread including links to past threads and posts on oil coolers.

I'll start with this ......

The red and blue colours denote coolant temps,
The long thin pipes are the tranny line connections.

http://www.ausjeepoffroad.com/forum/...1&d=1259193987

See... there's more to a vehicle conversion than simply swapping the steering gear to the other side! :D

Going by that pictorial display, the US version's auto fluids are "exchanging heat" in the coolest section of the radiator whereas, the Oz variant is trying to "exchange heat" in the hottest section surrounded by the engine coolant straight out of a hot motor... that's been well though out eh? :rolleyes:

In a nut shell... if the coolant surrounding the transmission oil "heat exchanger" is at a higher temperature there can be NO reduction in transmission oil temperature, thus an external aftermarket transmission cooler should be considered a "must have" item for a vehicle getting lots of use in a multitude of weather/driving conditions, the ONLY benefit I can see with this configuration is a quicker warm up period for the transmission :mrgreen:

Very interesting there Carves....

Got a new cooler on the way but when routing it should the radiator be bypassed altogether? i was origionally going to still use the radiator and flick the old cooler but now wondering if its better to run the coolers in series and bypass the rad altogether? Thoughts anybody? my head hurts? :wall:

Great idea for a thread! I've added it to the XJ modifications sticky under "Oil coolers"

Just my opinion .... but you need a gauge so you can see whats happening now ... and what happens after you make changes.

Factory stated "normal" temps are 50'c - 80'c ... Im getting average 75'c temps with two crappy factory aux coolers bodged together and the radiator bypassed.

Its only a temporary keep it on the road set-up ... and doesnt perform well in overdrive - on hills or towing ... Overdrive of course, is not the gear to be using in those conditions ;)

The following is a collection of threads originally posted to resolve a particular persons problem.

As with all threads ... there is an excellent collection of incidental info by the responding posters.

By reading all available info it is fairly easy to gain the knowledge and insight needed to make a decision on how, what, why ... and even why bother with ... cooling the XJ AW4 gearbox.

Will add more links as they are found/posted





AJOR General XJ Threads ... http://www.ausjeepoffroad.com/forum/...play.php?f=123

Auto Trans fluid boiled - 4l 96 XJ 4 speed ... http://www.ausjeepoffroad.com/forum/...ad.php?t=91612

Anyone else annoyed with there oil coolers? ... http://www.ausjeepoffroad.com/forum/...ht=oil+coolers

Auto transmission troubles ... http://www.ausjeepoffroad.com/forum/...ht=oil+coolers

Finally bought an XJ! Cooling issues already hahaha! ... http://www.ausjeepoffroad.com/forum/...ht=oil+coolers

Auto transmission lines to cooler? ... http://www.ausjeepoffroad.com/forum/...ht=oil+coolers

Auto transmission temp gauge ... http://www.ausjeepoffroad.com/forum/....php?p=1005757

Auto Transmission cooling Thoughts ... http://www.ausjeepoffroad.com/forum/...ht=oil+coolers

XJ for towing ... http://www.ausjeepoffroad.com/forum/...ht=oil+coolers

Trans temp guage ... http://www.ausjeepoffroad.com/forum/...ad.php?t=92110

Auto overheating at 110kph? ...http://www.ausjeepoffroad.com/forum/...ad.php?t=94805

So where would you mount an extra oil cooler?

Depends on which cooler you get.

In front of the radiator ... Keeps it out of the mud a bit and shouldnt need an extra fan for slow speed work. Downside is it may restrict a bit of airflow at cruising speeds.

Or ....

Behind the front bar if you have space or behind the cross member like in gojeeps and a few other writeups. Airflow, mud and cooler size need to be taken into consideration again.

Behind the bar OR in the space directly below the radiator would be pretty effective in relation to airflow I'd imagine...


Now obviously you can go "too big" when choosing a transmission cooler with the downside being a lower than specification transmission oil temp during normal operation, how well would a medium sized cooler with an additional thermofan either controlled by a thermal sensor and/or auxiliary dash switch address both temperature requirements?

carvesdodo... where did you fit your auxiliary transmission oil temp sensor & could a thermoswitch be placed there instead OR would a transmission oil line sensor like THIS one from Derale be better? :confused:

Hey Taz ... sorry for late reply ....

Im just using this .... http://www.ausjeepoffroad.com/forum/...7&postcount=11

So Im not really getting exact oil temps ... but close enough for my needs.

The unit also has a high temp buzzer and 12v power trigger for things such as thermofan relays etc ... It was just a quick, lazy way of getting a multifunction unit that did a number of jobs for me ... rather than dash full of permanent gauges and a gazillion extra miles of wiring / plumbing.

For an actual oil temp sensor ... Some have welded in sensor mounts in the sump pan ... It seems to be the recommended temp measuring spot. I was going to fit inline sensors on both oil cooler lines (another gunna :) ) but the electronic one is adequate - for me ... and easily hooked up to other components as required.

Nice... an LED display flickering between updates would be a royal PITA, brilliant little hack conversion though! :mrgreen:

Yes you're thinking is spot on... adding extra obstacles to the air flow through the radiator will inherently lead to raised peak temperatures, I suppose the best setup with the engine's cooling made a priority would be no oil coolers OR A/C condensers directly placed in the airflow's path towards the radiator... life without A/C in summer would be a little tough though eh? :D


EDIT: Aluminium has a lower thermal conductivity efficiency than copper, generally popular as a weight saving alternative... what is the CFM rating of those 3 thermo-fans you've got fitted?

I have been thinking of an engine oil cooler for awhile and had intended to try and fit inside the rh guard so as not to further inhibit air flow at the front of the vehicle. For the same reason I like the idea of mounting the transmission cooler behind the bumper (especailly for those of us with bull bars)

My XJ has already got a small davies craig oil cooler mounted in front of the radiator, as it get a bit hot in summer up here I was considering one of these oil coolers that have a small fan attached and run it off a temp switch. Has anyone fitted something like this or does it look too big to fit?
http://i786.photobucket.com/albums/y...sioncooler.jpg
http://i786.photobucket.com/albums/yy144/ad007e/tc2.jpg

I looked at buying one of those exact coolers, i found it was alittle to thick for where i intended to fit it just below the radiator. It would have came very close to the engine.
The b&m oil coolers with thermo fan are alittle thinner so easier to fit and their bar plate design is alot more efficient then the tube design of those coolers. B&M however are also more expensive then the Derale coolers but id rather buy from a brand i have used before and trust when it comes to keepimg the auto working nicely.

Whilst going over the XJ today I thought I'd grab a picture of what Chrysler thinks is sufficient to cool the AW4 transmission when towing, FWIW in person it's about 1/3 the size of what Davies Craig recommend for an aftermarket upgrade (part #678)

http://img197.imageshack.us/img197/6917/img0885yh.jpg

http://img39.imageshack.us/img39/451...cooler678i.jpg

land rover by comparison......
 

I've had quite a few land+range rovers and they have external fluid to air cooler auto trans coolers and then fluid goes via thermostat into "hot " side of radiator or back to transmission they also have a thermostat that stops fluid from going to getting cooled at all, further they also have an engine oil cooler in the cold tank of the radiator, and a fluid to air transfer case cooler.......this full house of coolers are fitted in vehicles that are meant for hot climates......for cold climates they run things differently, to keep fluids warm enough.....i had a range rover and a discovery which had electric elements in the windscreen glass ( not copper printed!) and the discovery had a separate diesel interior heater that could be run while engine was off! scotland is cold! ......truth is Rover builds all sorts of climate specific cooling (and heating) arrangements.....that's one sad point about jeeps, they're pretty basic- nice and simple which is a real plus point really!, but cheap for parts by comparison.

Well I've semi mounted the transmission cooler in the only place available (once I tossed the original Jeep one) partly in front of the radiator but 90% below sitting in the air flow from the bull bar vent through to the engine bay (via cut outs below radiator), according to Davies Craig line orientation isn't a big deal so this should work relatively well (I hope) and still have sufficient room for an aftermarket (motorcycle) thermo fan if necessary :D

A few different angles from the camera shoved under the bullbar :)

http://img196.imageshack.us/img196/920/img0899c.jpg http://img683.imageshack.us/img683/6208/img0904w.jpg
http://img138.imageshack.us/img138/8315/img0902.jpg http://img189.imageshack.us/img189/7053/img0901s.jpg

Yes you may have noted it's off-centre somewhat... that'd be because of the front chassis "cut outs" the cooler is sitting directly in front off ;)


EDIT: well it's been properly fitted for 5 days, flaring the ends of the pipe sections (with the tip of a closed pair of pointy nosed pliers) and fitting 2 hose clips to every connection (opposing clamp configuration) has been very effective at preventing leaks in the transmission lines... highly recommended, it also appears to be keeping the transmission more adequately cooled with sufficient airflow being directed through the factory bullbar's lower intake venting (mounting in front of a factory frame/chassis cutout would also be contributing to effectiveness) :mrgreen:

To maximise the flexibility of this cooler I installed it in series with the existing heat exchanger (located in the hot side of the radiator), thus the transmission wouldn't spend longer below recommended operating temperatures than necessary yet had a greater capacity to reduce the transmission oil before returning to the AW4 transmission, thanks to carvesdodo for the doing most of the graphical leg work :D

http://img710.imageshack.us/img710/7...ssioncoole.jpg


Additional post note: After traveling up to the Victorian/NSW border and back I can say without reservation this configuration made a definitive impact on improving the transmission operating temperatures even in what I would consider extreme sweltering conditions, my method of comparison was as "unscientific" as you can get utilizing the sensor pads in the tip of the fingers, crazy you say? not at all... previously whilst motoring about town the transmission shift lever would get "so hot" as to be untouchable, after the #678 had been fitted the hottest it reached was extremely warm and seeing as the shift lever is in contact with the transmission heat would obviously be radiated though it as well ;)

Future planned upgrades

• Motorcycle thermofan for #678 (and auxiliary switch)
• Method of monitoring transmission temperatures

Trans Cooler Install AW4
 

I am going to install the Craig Davis P/N 678 cooler and a VDO gauge to the XJ AW4 Trans. I have done the search and I am now totally confussed with all the opinions on how to install the cooler. Can someone please give me the best way to install the cooler. Some threads say run the Radiator trans cooler first and some say run only the new cooler. Others even say run the OEM cooler and the new Cooler. :wall: :wall: PLEASE HELP.:wall: :wall: :wall: :wall:

is the vdo gauge sender going in the sump or in the cooling line?
I vote for trans cooler first then radiator cooler and keep the oem air cooler for the power steering a la gojeep.
1. this helps the trans reach operating temp quickly in especially in winter
2. Seriously hot oil temps of 105C+ will still lose heat in the radiator

I don't like the idea of bypassing the radiator cooler unless there is an independent fan on the aftermarket oil cooler.

....take cover hear come CARVS....

Ps I have the gojeep oil cooler (about $80 landed in Australia at the moment)and taurus fan and it works great,
trans sump temps are mostly 80 occasionally gets to 90 yet to see 100.
I am sure that there are other ways of doing it that will also work.
Good luck with it.
http://www.summitracing.com/search/?...FLX-4120&dds=1

Thanks for the info Rainman. I did read the Go-Jeep write up and it did make alot of sense. I do still have the viscous fan on mine and was wondering can I still run the cooler in the same position as Go-Jeep and acheive the same outcome. Secondly did you manage to purchase the Cooler from an Australian Supplier. Cheers

I got mine from summit racing in the states.

I like the idea of a cooler that is not quite as long as the one gojeep used, in the same place and with a fan in front of it.

Although I have not tried it.

http://img710.imageshack.us/img710/7...ssioncoole.jpg

I installed the Davies Craig #678 cooler in this configuration because...

• The plumbing was easier
• I wanted faster warm up times for the transmission oil (reduce cold operation wear)
• The oil cooler assists the radiator via the transmission heat exchanger located in the radiator "hot" tank
• The coolest possible oil was in the return line to the transmission

More details can be found in the thread titled Oil Coolers ... XJ nescessities ??? :mrgreen:

Hey Taz. Thanks for the very benificial info and feedback from your own system.I will set mine up as per your specs. Can you confirm if you still run the Viscous fan in the xj.

with this set up what sort of daily/average operating temp do you get in the sump?
I have mine the other way and it sits mostly 70 -80, occasionally will hit 90

No actually the previous owner fitted a thermofan (bloody noisy) unsure of the CFM figure but I'd be tempted to "retro fit" a clutch fan should I come across one at the wreckers (I have no fan shroud fitted either) ;)


I have no temperature monitoring device for the transmission, however I can tell you the "shift" lever shaft that on occasions became too hot to touch now only gets very warm, I do plan on fitting a temp sensor in the future and am leaning towards the unit trialled by carvesdodo in the thread previously linked (OR a basic VDO configuration) ;)

My preference is to get rid of the radiator oil cooler all together to reduce the total heat load on the engine cooling system.
When off load, the oil passing through the radiator can also reduce the avaliable thermal capacity of the oil cooler for the transmission, as you are effectively using it as a heat exchanger for the engine cooling system. (Which should be up to scratch to not need the oil cooler to help it cool down).

The number one killer of transmissions is heat, my philosohy is to keep them as cool as possible, especially on slow moving vehicles. They need all the help they can get with their inherant lack of free airflow.

In the cars I have built, we have found that it is beneficial to have the transmission cooling system seperate to the engine cooling system for this reason. The Trans-Am Firebird we built benefited greatly with two big trans coolers in place of the radiator oil cooler, we not only saw much cooler trans temps (the box was built to handle up to 700Hp) but also saw cooler temps from the worked 351 Chev we squeezed into the engine bay.

In Australia, most of the time the climate will allow the box to heat up quickly enough anyway. On my supercharged Levin import (and the N/A race car), the manual gearbox doesn't have a thermostat on the oil cooler and it has no dramas with spinning the synchros up quick enough when cold.

Just my opinion anyway... :)

I guess it depends on what climate you're basing your primary requirements on... we live in a relatively cold section of Victoria that experiences regular cold weather patterns (with the odd heat waves tossed in too) hence the compromise between a "stand-alone" transmission cooler and an "in-series" configuration, as I stated earlier I went for the OEM->DC set up because the plumbing was the easiest (with the available tubing) I may experiment down the track with the opposite arrangement with the radiator's heat exchanger more directly regulating the returning transmission oil's temperature ;)

If you do that, you'll be heating your cooled oil back to the temp your engine cooling system is running at..... :)

You can buy inline thermostats, they bypass the oil cooler when cold, and allow full flow when hot. That way you get the best of both worlds, quick warm up, and no heat loading across cooling systems.

I looked for the inline thermostat can not find one. any idear where to get them from?
I think some of the adrad trans oil coolers have them built in.

http://adrad.com.au/performance/Adra...ance.Catalogue[Oct.09].pdf

1. To control the amount ATF (Auto Transmission Fluid)
bypassing the stacked plate core. The oil passes
through a self-regulating orifice which monitors
resistance to flow.
2. Controlled by viscosity, cooler, thicker ATF is
returned directly to lube through two open bypass
plates positioned above the stacked plate core.
3. As operating temperature increase, more
ATF flow is directed through the core with its
minimal flow resistance.
4. The result, a highly efficient oil cooler that
protects against lube system failure and
delivers optimal heat transfer as required.

There's a company called Perma-cool that makes remote oil thermostat assemblies, one retailer I noted stocking them locally was rocket industries ;)

Not entirely, returning via the radiator's heat exchanger will the increase transmission oil temperature but not to precisely the same as the engine coolant there will be a variance, adoption of configuration depends entirely on local environmental conditions ;)

Has anyone contemplated fitting a flex-a-lite (or similar) engine oil cooler kit to their XJ? :confused:

http://img137.imageshack.us/img137/7...sl500aa280.jpg

http://www.flex-a-lite.com/auto/html...l-coolers.html


I figured it might be yet another means to control the notorious XJ's running temperatures, I've still got the old tranny cooler so all I'd need is the plumbing and adapter plate, so any thoughts? :D

I thought those things were for either high performance n/a engines, or turbos.
our moters ain't high performance(unless you have spent serious $ on the moter)
I see were you are coming from in terms of another heat sink.
But as I have read it;
a new radiator, with a working thermo fan clutch, water pump and thermostat fixes 80% of the over heating problems, add a good electric fan in place of the belt driven one, 90% of the problems, add in a good size after market tranny cooler- in pretty much any configuration- and that is it, overheating "problem" solved.
and that is before the 12mm bonnet lift that costs bugger all and is apparently effective.
Don't get me wrong, I'm not saying do not do it, I will be the first to ask for pics, It's just as I see it the "XJ overheating problem" is a known weakness, with a well established solution.
So you asked for thoughts and that is my 2Cents.
Good luck with it and do post the results ................with pics.

That being said, mashed67 is building an engine that needs 36lb/hr injectors so he is gonna need all the cooling he can get.
Regards.

Have thought about the engine oil cooler and whilst i have been too lazy to follow up on it I also believe it is a very good idea. The advantage of oil cooling is that many parts of the motors that are under enormous strain (just think about the big ends and crank journals) actually get some form of cooling. I would think very beneficial to a motor working hard in a confined space with little air passing it.

Baaahaaahaaa .... Its all good rainman .... **)

All the adhoc methods work to varying degrees ... There is just so many that dont provide any data in regard to before and after results. If they all did ... they wouldnt be adhoc methods.

Im still only running two crappy XJ factory coolers with the heat exchanger bypassed ... blasted xmas and moving house :wall: ... Recorded temps are still averaging 70'C as long as I keep it out of overdrive .... Thats low range / highway / and towing results.

I dont doubt the actual oil temps are slightly higher as Im only measuring the sump housing temp ... not the oil.

As a comparison ... the sump housing is now up to 30 degrees cooler than what it used to be in the standard factory configuration.

So big bling, imported coolers arent an absolute nescessity .... just a better quality / properly made one - than the pathetic thing provided. ;) ... With the exchange rate at the moment ... importing is perhaps a consideration.

I Will be fitting a std 6cyl auto falcon cooler for a comparison when the damn rain stops out here and will provide the temps that that cooler provides .... Then I will be fitting a 678 davies craig unit as I believe that will be more than satisfactory ... and locally available for easy replacement if damaged. The others I have here are big enough and work well under testing ... but I dont know what they came off so are of no value in regards to info for others.

The idea being that finally .... someone will have provided some before and after results with a variety of setups in different operating conditions ... so individuals will be able to make a decision using the results ... and their needs ... rather than relying on the guesses posted on a private web site as being the ultimate answer :rolleyes:

In fact Im really really surprised that the difference between US and Oz heat exchanger placement in the XJ wasnt picked up on and posted on the net ... long before I started taking an interest in what I was driving :rolleyes: .... I'm pretty sure if it had ... it would have led to a completely different approach to the issue.

Hence the reason that those who support the ... aftermarket oil cooler first - then the XJ heat exchanger set up ... without fitting a temp gauge NEED the biggest cooler they can lay their hands on ... in the hope it cools the oil enough so the engine coolant temp doesnt affect the benefits of the new oil cooler tooooo much ;)

Not having a go at you Taz .... Doing it that way is a fairly safe way of getting some cooling without using a gauge to confirm results. I would rather have the gauge first ... see whats happening temp wise ... and then know how well I had fixed the issue going by the new operating temps.

Lots of aftermarket coolers have built in bypasses for initial startup / cold climate operation. The thermostat versions sound good ... but again ... a temp gauge would be needed to ensure the the thermostat was always functioning correctly .... just like the engine coolant thermostat with its stuck open / stuck closed issues.

Its also worth considering repeated comments over the years about how hot the AW4 box gets compared to other autos .... Having read plenty of them over the last 18mnths on the web ..... I really dont think the AW4 is like an old GMH 3spd slushmatic that had to be left idling in the driveway for 10min during winter in Tumut or Omeo ... Personally I think the cold climate operation comments / concerns really ought to be left on the north american forums where they belong ....... Our cold weather is a joke by comparison to theirs.

I knew it was only a matter of time before you jumped in on this one Carves...

Now why would we want actual data, isn't anecdotal evidence good enough????

I agree with the cold weather issue I think that you are spot seeing that these are used in the icy winters of North America and Europe though as you mentioned the cooler is plumbed differently.

I myself have an alloy Landrover cooler plumbed in between the radiator and the factory cooler, not to fix a problem but as an enhancement for towing duties...

Hey Terra, where did you get a 351 chev from?????

Hey Carves, Apreciate what you have stated. I have just purchased an oil temp gauge and will fit it to the Trans Sump ASAP. My XJ still has the Standard Jeep Cooler Setup. I want to see what the temps are at present before I get the New Cooler Setup. I will keep you posted with the results.

Let us know how you go with the temp testing both before and after and if possible can you include ambient temperature as well or at least try to test both on similar temp days and similar times of the day if possible to try and get a reasonble comparison....