Tranny cooler woes

I have fought with this problem long enough. 1996 AW4/NP231, 4.88 gearing

My engine runs cool, never overheats. The tranny runs cool on the road but as soon as I get in stop and go or I'm crawling along a trail it gets too hot.

I have tried both the tube and fin Hayden(30,000GVWR RV cooler) and the stacked plate Hayden(30,000GVWR RV cooler) both were run 2/3rds to the pass side. I have a ZJ fan clutch and factory electric fan.

I think its just not getting enough flow across it. I'm looking at a Derale cooler, 26" long, that I can mount on the front of the cross member and behind/protected by my Logans winch bumper.

I have a B&M tranny temp gauge with senders on the inlet/outlet of the cooler to check its efficiency. The past coolers have worked okay but 220* on the downstream side is unacceptable to me. If its reading 220* on the downstream I'm usually getting 260* at the inlet of the cooler. This is in moderate weather, mid-high 80's.

This is the cooler I'm looking at;http://www.summitracing.com/parts/der-13266/overview/

It will get flow from the fans pulling and the wind off the road surface.

Thoughts?

Short of finding room for a cooler/fan combo(good luck there huh!) I really do not know how to get this thing to cool any better than what I have tried.

220* on the return side sounds really high. I run an almost identical cooling setup to you and usually I only see temps like that on super long uphill climbs with tons of wheelspin and slow speed (no airflow). When wheeling I am generally at 180* on the return side or less. Has it always run that hot and how old is the fluid?

Sounds like something is wrong.....those temps are too high. I have been running a 30,000 GVWR cooler for years and never an issue. I live in SoCal too where ambient temps can get up there.

Maybe you have a torque converter locking issue....just a guess since most trans temp issues are torque converter related.

the_weirdo said:

220* on the return side sounds really high. I run an almost identical cooling setup to you and usually I only see temps like that on super long uphill climbs with tons of wheelspin and slow speed (no airflow). When wheeling I am generally at 180* on the return side or less. Has it always run that hot and how old is the fluid?

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I flushed it out the last trip last summer before it got cool out side. The filter has less than 5000 miles on it but is 5 years old. I'm getting ready to swap it.

The fluid does not smell burnt at all and is only slightly dark, still has a red tint to it.

I have 3 more XJ's and a MJ with the same set-up that all run cool but I do not wheel them and my trail rig runs cool except for in stop-n-go and on the trail on steep climbs.

It slowly climbs up in temp and it is not fast about dropping either.

cracker said:

Sounds like something is wrong.....those temps are too high. I have been running a 30,000 GVWR cooler for years and never an issue. I live in SoCal too where ambient temps can get up there.

Maybe you have a torque converter locking issue....just a guess since most trans temp issues are torque converter related.

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How do I check that? It shifts fine. I run it in 1/2 and 4-low/2-low(Tera 2 low kit) while on the trail. It runs cooler in 1/2 than it does in 3 on the trails.

At no point has the tranny felt like its getting ready to go other than the temp is high. I'm wondering if the gauge is bad.

xjtrailrider said:

How do I check that? It shifts fine. I run it in 1/2 and 4-low/2-low(Tera 2 low kit) while on the trail. It runs cooler in 1/2 than it does in 3 on the trails.

At no point has the tranny felt like its getting ready to go other than the temp is high. I'm wondering if the gauge is bad.

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Hmm... Do you ever burp fluid?

A few years back, cal and I were working on my MJ that we converted from a Peugeot to an aw4 and were working on the torque converter lock up....it wasn't working so cal wired a switch with an led so we could manually lock the torque converter and the led would light up when it was working.....check some wiring diagrams and see which one to do but it was easy for us to diagnose....well mike Rollins figured it out and it was because the switch on the floor pedal wasn't adjusted right. :/

I use a fan forced transmission cooler that is mounted on top of the front skid plate. The fan is controlled by a thermoswitch. Before anyone says "aint no room", I did move the skid down 3". This was done, at first, because a stock front skid on a lifted Heep is fairly useless. It is way too high to protect the steering. Or anything else for that matter...

With the skid dropped the 3" it allowed the transmission radiator to be mounted on 1/2" spacers. The flow routing is: transmission to aux cooler to Heep radiator and back to the transmission. I run it through the radiator as it snows here. Helping to get the transmission up to temperature is a good thing. The thermoswitch on the fan prevents over cooling the transmission.

Thermoswitch is a Derale. 180F on 170F off in operation.

The cooler is a stacked plate from an F350 and the fan I had laying about the house.

cracker said:

Hmm... Do you ever burp fluid?

A few years back, cal and I were working on my MJ that we converted from a Peugeot to an aw4 and were working on the torque converter lock up....it wasn't working so cal wired a switch with an led so we could manually lock the torque converter and the led would light up when it was working.....check some wiring diagrams and see which one to do but it was easy for us to diagnose....well mike Rollins figured it out and it was because the switch on the floor pedal wasn't adjusted right. :/

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No, it has never burped any fluid out even if I overfill it a bit.

O-Gauge Steamer said:

I use a fan forced transmission cooler that is mounted on top of the front skid plate. The fan is controlled by a thermoswitch. Before anyone says "aint no room", I did move the skid down 3". This was done, at first, because a stock front skid on a lifted Heep is fairly useless. It is way too high to protect the steering. Or anything else for that matter...

With the skid dropped the 3" it allowed the transmission radiator to be mounted on 1/2" spacers. The flow routing is: transmission to aux cooler to Heep radiator and back to the transmission. I run it through the radiator as it snows here. Helping to get the transmission up to temperature is a good thing. The thermoswitch on the fan prevents over cooling the transmission.

Thermoswitch is a Derale. 180F on 170F off in operation.

The cooler is a stacked plate from an F350 and the fan I had laying about the house.

Click to expand...

Yep I saw your set-up in a search. i like it but I don't think its gonna work in my case. The stock engine skid interferes with my steering and bends the drag link at flex so I took it off.

I think your gauge is wrong or something.

All my friend and I ever had was a cooler from a Ford Explorer (stacked plate) plopped right in front of the AC condenser.

He had a gauge on his. Never got over 180º while wheeling IIRC, and he had 4.10s on 35s.

I never had a problem with mine. 4.88s on 35s.

I used a cooler/fan combo on my jeep. I got rubber line running from the trans to thr cooler that is mounted to my hood(yes, my hood). I got a 8in diameter hole cut in the passenger side of my hood where the cooler sits. The fan sits outside the hood with the cooler underneath. The fan is set up in a pull so It also helps to pull heat from the engine bay. Right now the fan is hooked to a toggle switch but will eventually have a thermal switch so I don't have to worry about turning it on in high stress driving situations.

MoparManiac said:

I think your gauge is wrong or something.

All my friend and I ever had was a cooler from a Ford Explorer (stacked plate) plopped right in front of the AC condenser.

He had a gauge on his. Never got over 180º while wheeling IIRC, and he had 4.10s on 35s.

I never had a problem with mine. 4.88s on 35s.

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I'm with this guy. I've got a small like 6x9" cooler on the front of the condenser right in front of the mech fan. The only time I saw really high temps was doing 30+ mph in soft sand on a 90*+ day for like 5 miles straight. The engine and trans both overheated at the same time, I was working them pretty good. Other than that, never been over maybe 200* and that was hard wheeling on a hot day with virtually zero airflow other than the fan.

Gotta agree, the only time mine has ever been that high (with a B&M gage also) was on a long slow steep hill climb at Harlan, and the engine temps got very high too. Normal wheeling/stop and go I never get above 180/190. Ive got a smaller 6x10 or 6x12 cooler on mine from Napa. I pulled my popup camper almost 900 miles round trip (with some long mountain pass pulls) with my wheeling rig to the Crawl (July, 90 degree heat) last year, and never had issues. Id confirm the gage is good, and start trouble shooting.

Any chance pulling air from under the hood is the issue. It get considerably hotter than that underhood. If the air doing the cooling is hotter than the fluid .... Not a lot of cooling going on.
A cheap test would be to pull the cooling air from the outside and blow INTO the hood. Otherwise at those temps you should be starting to see signs of trans failure. I would suspect the guage as well.

MoparManiac said:

I think your gauge is wrong or something.

All my friend and I ever had was a cooler from a Ford Explorer (stacked plate) plopped right in front of the AC condenser.

He had a gauge on his. Never got over 180º while wheeling IIRC, and he had 4.10s on 35s.

I never had a problem with mine. 4.88s on 35s.

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I need to get a infra red gun and double check the sending units.

bluejeepkid said:

I used a cooler/fan combo on my jeep. I got rubber line running from the trans to thr cooler that is mounted to my hood(yes, my hood). I got a 8in diameter hole cut in the passenger side of my hood where the cooler sits. The fan sits outside the hood with the cooler underneath. The fan is set up in a pull so It also helps to pull heat from the engine bay. Right now the fan is hooked to a toggle switch but will eventually have a thermal switch so I don't have to worry about turning it on in high stress driving situations.

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I want to see your setup. I have a Hayden stacked plate/fan combo brand new never used but I cant find a spot big enough to put it. How about pushing the air down onto the cooler? Would that work better and still push the hot air out of the engine bay?

sunburned said:

I'm with this guy. I've got a small like 6x9" cooler on the front of the condenser right in front of the mech fan. The only time I saw really high temps was doing 30+ mph in soft sand on a 90*+ day for like 5 miles straight. The engine and trans both overheated at the same time, I was working them pretty good. Other than that, never been over maybe 200* and that was hard wheeling on a hot day with virtually zero airflow other than the fan.

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My DD has 4:10/30's and dual XJ e-fans and i never see it over 150 on the hottest days. I'm running the same cooler as my trail rig. This is a 90 RENIX and they tend to run a bit hotter than the HO

stumpXJ said:

Gotta agree, the only time mine has ever been that high (with a B&M gage also) was on a long slow steep hill climb at Harlan, and the engine temps got very high too. Normal wheeling/stop and go I never get above 180/190. Ive got a smaller 6x10 or 6x12 cooler on mine from Napa. I pulled my popup camper almost 900 miles round trip (with some long mountain pass pulls) with my wheeling rig to the Crawl (July, 90 degree heat) last year, and never had issues. Id confirm the gage is good, and start trouble shooting.

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Agreed

Devilfrog said:

Any chance pulling air from under the hood is the issue. It get considerably hotter than that underhood. If the air doing the cooling is hotter than the fluid .... Not a lot of cooling going on.
A cheap test would be to pull the cooling air from the outside and blow INTO the hood. Otherwise at those temps you should be starting to see signs of trans failure. I would suspect the guage as well.

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I'm with you on this!

xjtrailrider said:

... The tranny runs cool on the road but as soon as I get in stop and go or I'm crawling along a trail it gets too hot.
...
I have tried both the tube and fin Hayden(30,000GVWR RV cooler) and the stacked plate Hayden(30,000GVWR RV cooler) both were run 2/3rds to the pass side. I have a ZJ fan clutch and factory electric fan.

Click to expand...

I am concerned about 2 things:
1. The location of your transmission cooler, and
2. The orientation and direction of fluid flow through the cooler.

1. You say you mounted the cooler 2/3 of the way to the passenger side. I hope that means it is in front of the main opening of the mechanical fan -- not so far to the side that the fan's hub is blocking airflow, and not so near the middle that much of the cooler is blocked by the shroud. Yes, I know the cooler is mounted in front of the A/C condenser and radiator, but still what's behind the radiator has a big effect on the airflow through various parts of the radiator.

Also, make sure the mechanical fan clutch is working properly -- it may be worn out so the fan never does pull much air through. One quick way of determining if the clutch is working is notice if you get a substantial roar from the mechanical fan when you first start up in the morning. If not, the clutch is no longer effective and needs to be replaced. On mine the roar is so loud that I cannot hear the engine or exhaust as I pull out of the driveway and head up the block.

2. As for orientation, you want to make sure the inlet is below the outlet, otherwise you just get a big air bubble in the cooler that never goes away and you get precious little cooling.

HTH

HappyDog

HappyDog said:

I am concerned about 2 things:
1. The location of your transmission cooler, and
2. The orientation and direction of fluid flow through the cooler.

1. You say you mounted the cooler 2/3 of the way to the passenger side. I hope that means it is in front of the main opening of the mechanical fan -- not so far to the side that the fan's hub is blocking airflow, and not so near the middle that much of the cooler is blocked by the shroud. Yes, I know the cooler is mounted in front of the A/C condenser and radiator, but still what's behind the radiator has a big effect on the airflow through various parts of the radiator.

Also, make sure the mechanical fan clutch is working properly -- it may be worn out so the fan never does pull much air through. One quick way of determining if the clutch is working is notice if you get a substantial roar from the mechanical fan when you first start up in the morning. If not, the clutch is no longer effective and needs to be replaced. On mine the roar is so loud that I cannot hear the engine or exhaust as I pull out of the driveway and head up the block.

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That is correct, the majority of the cooler was in airflow from the blades of the fan. I have a new ZJ heavy duty fan clutch

HappyDog said:

2. As for orientation, you want to make sure the inlet is below the outlet, otherwise you just get a big air bubble in the cooler that never goes away and you get precious little cooling.

HTH

HappyDog

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This could be an issue. I will double check the routing.

If I run a under hood mounted cooler(fan on top of the hood pushing air in) will the tranny be able to push fluid up to that height and will I have issues with rain water hitting the engine components. If I put it on the pass side then the ignition is there, If I go with the drivers side then there is the CPS/MAT/TPS/MAP all in that area, what will the water do to all of these electronics?

xjtrailrider said:

...
If I run a under hood mounted cooler(fan on top of the hood pushing air in) will the tranny be able to push fluid up to that height

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It will have no problem pushing it up that high -- it's only an inch or two above the radiator outlet, and I got first-hand experience with what vigor the transmission pushed the fluid out of there while in Park!

xjtrailrider said:

and will I have issues with rain water hitting the engine components. If I put it on the pass side then the ignition is there, If I go with the drivers side then there is the CPS/MAT/TPS/MAP all in that area, what will the water do to all of these electronics?

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I don't know, but I am not enthusiastic about the idea. Especially because when the Jeep is driven at speed the top of the hood is in a low-pressure area so the fan will be battling the natural airflow.

Let's be totally weird -- what about putting a flat turbine on the hood? Just like the ones to exhaust the attic, but much smaller? Rain doesn't get in, it lets the heat out, and when there's wind it sucks the heat out rapidly. Just need to get one rated for 90mph or so...

Something that is similar but easier to find is a flat squirrelcage fan, like for a bathroom vent. They're 7-10" diameter and 2-4" high, and have all the desirable attributes of the turbine fan.

Time to do some experiments! But I'm fully booked up with my own issues...

I'll get pics as soon as I can of my setup. And no, I dont think having the fan push air inside the engine bay would be possible. Maybe at slow speed crawling, but definitely not at any decent speed. The fan would have to fight against the natural air flow thru the engine bay.

xjtrailrider, have you made sure that there is no air-flow blockage in the area the transmission cooler is mounted? Sometimes the A/C condenser and/or radiator gets plugged up with mud, insects, or whatever. Please give it close scrutiny.

HappyDog said:

xjtrailrider, have you made sure that there is no air-flow blockage in the area the transmission cooler is mounted? Sometimes the A/C condenser and/or radiator gets plugged up with mud, insects, or whatever. Please give it close scrutiny.

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Other than my winch, there is no blockage of air. I'm running a 3-row radiator that is fairly new. I don't run mud in my Jeep, just rocks.