Tranny Cooler Installation

I bought a Hayden tranny cooler and was wondering should I completly bypass the radiator or mount it inline with the radiator?

In Line!!

Always install IN THE LINE TO the stock radiator trans cooler. The trans needs to warm up quickly as much as the engine does and this helps to assure that. I am aware some have bypassed the stock cooler but is totally not advisable.

When you examine your radiator you will find two lines attached to the ATF cooling in the radiator. The "hot" fluid goes in the upper locaiton, and the cool fluid come out the lower fitting.

On the Mopar Aux Trans cooler they have you disconnect the lower line and place the aux cooler between the lower fitting of the radiator cooler and the rubber line.

You will need to examine your connector, if it has plastic ears sticking out then you will need to press those ears against the line and "pull". The connector will come apart. If it the new one then you will need the 3/8 AC line tool to push back the springs then you can disconnect.

ATF fuild should flow Trans -> radiator trans cooler -> Aux trans cooler -> Transmission.

why do you say to keep the factory cooler in the loop?
if heat is a problem for installing the aftermarket cooler, why not bypass the radiator?

I saw the explaination about warm up, but what about running temp.?

you woulb be transfering the heat from the coolant to the trans. fluid or vice versa depending on what is hotter.

anaheimxj,

The reason you install the Aux cooler is to get heat out of the ATF. On my 88 XJ you can tow up to 2000 lbs without an aux cooler but my owner's manual says with the aux cooler you can tow up to 5000 lbs.

Lets say our XJs weight 3500 lbs, with a trailer attached engine, transmission, and rear axle are moving more than two times the normal weight of the vehicle.

For most people who never tow the factory set up will meet their needs with no problems. If you are one of the few who tows you will need a larger cooler because of the larger load on the drivetrain. Also keep in mind my 88 XJ says if you tow you have to change the ATF every 15,000 miles, if you don't tow it every 30,000 miles.

Heat transfer is more of an art than a science. You can calculate what size heat exchangers you need for the most extreme conditions but you have to do tests to verify you choose correctly. I am more than willing to say the AMC engineers who designed my 88 XJ spent the time to figure out what aux cooling was required. Remember they sold the vehicle and said if you have all this equipment in the owner's manual then you can tow up to 5000 lbs and be covered by the warranty.

Also keep in mind winter and the engineers took that into account so the transmissoin fluid does not get too cool in winter. It is a balancing act. The solution provided it the best solution for the north american market. If the XJ was designed for a different operation temperature range the radiator and trans cooler would be different sizes.

We all need to keep cooling system maintenance in mind. If you plan on towing and your XJ more than 5 years old I would replace the radiator, radiator hoses and install an aux cooler if you plan to tow over 2000 lbs. With all that you should not have a problem.

If you are worried you can install a temp sensor in one of the trans cooler lines and monitor it. I see GM now has a trans fluid temp gauge on some of their trucks.

If you plan to tow over 2000 lbs then get an aux cooler, the OEM cooler is 48 sq in., and change the ATF fluid every 15,000. With that your XJ should run just fine.

Martin

Listen well about that trans cooler. This treads pretty funny cause we towed a pop-up camper up to North Ga./Tenn from Florida and blew a trans line in macon and after fixxing the line proceeded to blue ridge. Seems that the trans was marginal when we left Florida (176K) Trans went bad and would overheat badly when we went over 55mph. Lucky it was the practice run for the Crawl coming up. Got to leave the camper in N. Georgia so atleast we wont have to tow it up there. Wish I had read this sooner.

Correct, balancing act-

You want the trans to operate in a narrow band of temperature- just like the engine. If operating in really cold temps the cooler in the rad will actually work to help to keep the trans warmer. This is why the installation of the cooler before the rad cooler. Yes you could sit down and calculate trans needs and therefore the specific cooler but to take actual heat loading and cooler efficiency and being specific to airflow would be too tedius and time consuming. I have seen on here guys install a cooler so large it almost would not fit. That is totally unnecessary. If you want to see how much cooler the engineers saw fit to include with their UC option, it is so small it is kinda hard to see- about the size of a power steering cooler on other vehicles. So, i'd choose something in between.

As far as when to change ATF, as soon as the fluid gets burnt. If really hard 4wheeling one afternoon burns it, change it when you get home. If burn it the very next time towing hard, change it then too. However if never pushed to the approximate 250 degree range, might never really have to change it. Is as simple as that. The ATF will last a long time if not overheated. However, if the trans is starting to get a little old and the torque converter or/and a clutch pack or two are not operating as efficiently as they used to- in other words slipping more between shifts and the like, check your fluid condition more often for burning even if the trans fluid overall is not pushed to that 250 limit. Is possible to have specifically localized overheating of the ATF that will still ruin it. Had a GM 6.2 Banks Turbo 700R4 trans ruin the fluid even though the aux cooler technically kept the fluid below 250 through the lines. It still overheated the fluid in that specific area because the converter was not locking up correctly- exceeded it's capacity.

So, I have a question...I want to install a aux tranny cooler, but I live in Alaska and we have problems up here with the aux cooler lines freezing in the winter time and overheating the tranny. So, when I install the tranny cooler, i should run it through the rad and then the aux cooler? - and that way when the engine is operating at 210 degrees and it flows to the aux cooler, the aux cooler with cool it down a bit, but it should still be warm enough to operate the tranny properly and prevent the lines from freezing??? i'd rather do it this way than put the aux cooler before the rad because i'll be towing during the summer months up here where it can reach into the 80s and i'm afraid if it went to the aux cooler first then the rad, it would be too hot once it got back to the tranny.

My understanding of this is that if you install the aux cooler before the tranny, it removes excess heat from the transmission fluid, then reheats the fluid to the nominal temperature. This avoids really hot transmission fluid from being cooled by your engines cooling system, and heats the transmission fluid to the proper temperature. This should cover both scenerios, summer and winter.

how is the jeep setup with the towing package from the factory? is the aux cooler before or after the rad??

Im pretty sure the factory aux cooler on my 96 is plumbed after the radiator cooler. So the fluid travels from tranny-radiator-aux cooler-back to tranny. That seems backwards from what I remember but its what the FSM says.

Looking at my previous post, and after I looked at a few sites on the web looking for install instructions. The general agreement between all the sites I looked at figure that heat is going to be the number one problem, and to install the cooler in the fluid return line (after the radiator). The thought is ' why heat up the fluid after you've cooled it? '

My thought is ' why dump the heat in the radiator when you could dump it in the cooler first? '

I suppose it's what your after that counts.

The OEM cooler isn't much to look at and not nearly as large as a Hayden or B&M unit.

I don't know, I suspect either would work. If you're looking for the most cooling of the transmission fluid, I suspect after the radiator will be the best.

Looking in the 95 FSM, the aux cooler is definitely after the radiator cooler. I'm trying to figure out the reason for this and haven't come up with many ideas. One is that it actually doesn't matter very much, so they flipped a coin. The other is that ideally the tranny fluid should be a little cooler than the engine coolant, especially under stress. If your engine is running hotter than the fluid should be, it would be a waste to cool the fluid first and then reheat it on the way back.

I think if I were in an extreme climate where freezing is possible, I would consider plumbing a bypass for the external cooler. I don't think that would be too hard. The pressure is not very high. A couple of tees, a piece of line, and a little ball valve would do it.