Tranny Cooler: Bypass or In-Series

[blairracd]

Treating the baby/the ***** to a transmission cooler because it’s hot as balls and hilly here.

I think I’m going with the Hayden 679. Question is, should I run it in line or just bypass? I’ve seen arguments for both and I are to dumb to discern which way I should go.

Thanks for your time and help.

 

[LittleCaesar]

In line as long as the radiator is not original. Look toward buying a B&M or Tru Cool cooler that has a LPD bypass such as a B&M 70264 or a Tru Cool 4544.

 

[Devbot]

If I'm not mistaken the proper set up is the cooler in line with the rad, so the auxiliary cooler removes any excess heat and the radiator then ensures it stays around proper operating temp. Or at least that's what made most sense to me in the arguments I've seen. If your rad is not OEM (which I would severely hope not at 20 years old) then there's not much reason to bypass it

 

[Honda pc]

I tbought the whole point of getting cooler was to bypass the radiator and prevent milkshake transmission oil destroying transmission.

I don't think having cooler transmission temp is big deal unless you're climbing hills or with heavy loads.

So why not bypass the radiator all together and have to never worry about milky transmission failure from radiator failure???



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[Doc2012]

Think about this.

The cooler is done for 2 reasons:

1) a way to avoid the pink milkshake

2) cool the transmission fluid.

Putting the cooler in series with the radiator completely negates the first reason of putting the cooler in in the first place.

Putting the cooler in series, trans, cooler, rad, trans, completely negates the point of having the trans cooler.

Putting the cooler in series trans, radiator, cooler, trans, just increases the fluid capacity, and doesn’t stop the pink milkshake.

Run it separately.


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[nissanh]

All Land Cruisers (I am aware 80 and 100) got an external cooler in series with the radiator.

 

[Devbot]

Putting the cooler in series, trans, cooler, rad, trans, completely negates the point of having the trans cooler.

Not true at all. The idea isn't just if your trans is producing too much heat the cooler will assist in managing it, but also if the cooler itself is too efficient and prevents the fluid from reaching operating temp (as plenty have noticed in colder weather, depending on the unit) then the rad will assist in warming it up back to where it should be. The rad almost acts as a regulator ensuring it would constantly hover around 180-200 at all times.

 

[Doc2012]

Not true at all. The idea isn't just if your trans is producing too much heat the cooler will assist in managing it, but also if the cooler itself is too efficient and prevents the fluid from reaching operating temp (as plenty have noticed in colder weather, depending on the unit) then the rad will assist in warming it up back to where it should be. The rad almost acts as a regulator ensuring it would constantly hover around 180-200 at all times.

Considering the ideal temperature for a transmission is 175°, plus or minus 25°, I don’t the benefit of it being in line with the radiator.

If you’re in severely cold climates part of the year; then a way to midi gate ‘too cold of fluid’ would be to cover the cooler; probably like you’re doing with the radiator at that point.

Otherwise; don’t run the cooler, and get a new radiator.

But that’s just me. [emoji2369]


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[gamefreakgc]

Not true at all. The idea isn't just if your trans is producing too much heat the cooler will assist in managing it, but also if the cooler itself is too efficient and prevents the fluid from reaching operating temp (as plenty have noticed in colder weather, depending on the unit) then the rad will assist in warming it up back to where it should be. The rad almost acts as a regulator ensuring it would constantly hover around 180-200 at all times.

Yes, the Tru-Cool I purchased that has the cold fluid bypass still said on the installation instructions to put it in series. It was a fairly large stacked plate design though so that might have been part of it as it had a very high BTU rating. A smaller tube and fin design wouldn't be as likely to keep the fluid too cold. My winter temperatures don't drop below 30 degrees though so I did not put mine in series. Heat destroyed the transmission before I bought it and the PO had a used unit installed so I knew real quick I needed to cool it down. It's consistently over 100 degrees in June-Aug here.

You'll know if you picked too big of a cooler if the transmission holds gears too long in cold weather in an attempt to warm up the transmission fluid. Not very common though unless your winters are very cold.

EDIT: Last thought about running in series or not: if you choose not to put it in series, run a length of hose capping the unused fluid ports. If the barrier between the coolant and previously used transmission fluid does fail, you definitely don't want that coolant just dumping on the road and leaving you dry!

 

[Romeo1]

All I did was replace the oem radiator with another OE Toyota and call it day.

I wheel and rally it pretty hard and is never been an issue, even slightly. Does 80mph on 32s and 4.30’s happily as long as it’s aired up……

I don’t tow with it, but that’s what my Cummins is for.

To be completely honest I’m not up to speed on why a 3rd gen outside of trying to prevent mixing of the trans and engine fluids is even necessary? Is it the 33s and bigger tires and the 4.10s that cause issues?

I’ve crawled around Moab and it was never an issue. Crawled around southern Idaho and never an issue. All in 4 low. But I do plenty of 50-60 mph 4wd stuff too, usually at 20 psi also. I don’t lug it, and I lock it in gear and rev it all the time.

I’m all for improvements, when it makes sense. I’m just not sure this is one of those times. My modding for the sake of modding days are over though. I’ve done plenty of senseless mods on trucks, sleds, and other garbage over the years that I’m just over it I guess. So I’m a bit skeptical on this one. Trans cooling has never been a issue for me.

I want schooling here. I’m just not seeing the point in adding to what the 130$ denso radiator seems to do perfectly in my very limited 4runner ownership experience.

 

[gamefreakgc]

All I did was replace the oem radiator with another OE Toyota and call it day.

I wheel and rally it pretty hard and is never been an issue, even slightly. Does 80mph on 32s and 4.30’s happily as long as it’s aired up……

I don’t tow with it, but that’s what my Cummins is for.

To be completely honest I’m not up to speed on why a 3rd gen outside of trying to prevent mixing of the trans and engine fluids is even necessary? Is it the 33s and bigger tires and the 4.10s that cause issues?

I’ve crawled around Moab and it was never an issue. Crawled around southern Idaho and never an issue. All in 4 low. But I do plenty of 50-60 mph 4wd stuff too, usually at 20 psi also. I don’t lug it, and I lock it in gear and rev it all the time.

I’m all for improvements, when it makes sense. I’m just not sure this is one of those times. My modding for the sake of modding days are over though. I’ve done plenty of senseless mods on trucks, sleds, and other garbage over the years that I’m just over it I guess. So I’m a bit skeptical on this one. Trans cooling has never been a issue for me.

I want schooling here. I’m just not seeing the point in adding to what the 130$ denso radiator seems to do perfectly in my very limited 4runner ownership experience.

You are right, a perfectly healthy cooling system with a new or near new radiator will provide all the cooling capacity needed. Our rigs are pushing 25 years old now though so heating issues are starting to pop up more and more. That's one of the main issues that kills all the 2nd Gen 4Runners and Pickups, overheating that leads to blown HG's. Not as bad on these 3rd Gens though. Many of us on here do have heavily modified rigs with extra weight, armor, accessories or in my case, extra power. Add on top of that a cooling system that's less than new and heat starts to become an issue as the transmission has to work harder.

With only a unmodified supercharger on mine when I got it, the transmission fluid was almost as black as the engine oil. It was burnt as burnt could be. Thankfully no damage to the stout A340F. A cooler wasn't optional for me if I wanted to avoid yearly transmission fluid changes.

 

[Brian.]

OP is in Missouri, bypass will mean the ATF won't *WARM* in the winter for any drive shorter than ~30 minutes. If you want to increase wear, this is a great plan... else doing as the OEM's do and running in-series would be the smart choice.

Obviously, if this is a full time crawling rig, only brought out to play on days with ideal temps, well... why would you be asking this question if you'd built one of those?

 

[sleepydad]

All I did was replace the oem radiator with another OE Toyota and call it day.

I wheel and rally it pretty hard and is never been an issue, even slightly. Does 80mph on 32s and 4.30’s happily as long as it’s aired up……

With only a unmodified supercharger on mine when I got it, the transmission fluid was almost as black as the engine oil. It was burnt as burnt could be. Thankfully no damage to the stout A340F. A cooler wasn't optional for me if I wanted to avoid yearly transmission fluid changes.

I messed around a lot with this a couple of years ago.

#1 unless you monitor your trans fluid temp during use your assumptions are most likely wrong. spikes in temp are very common.

even loaded rigs during hot weather do a pretty decent job of keeping temps under 250 f most of the time. the stock Toyota setup works pretty well most of the time.

before I did anything I pulled a trailer, boat all around 1000 lbs and yes this will run you a bit hotter but nothing over 250 f

if you wheel in the sand dunes in 4wd hi on even a cool day you will see temps in excess of 350 f or more. if you wheel in 4wd lo on that same day you will see much lower temps but still 300 f is not a surprise. crawling in Moab will also produce some nasty temps unless your in 4wd lo. The correct use of 4wd lo can make a huge difference in temps.

I did a larger (not in series with the radiator ) with a thermostatic bypass valve.

Amazon.com: Hayden Automotive 679 Rapid-Cool Plate and Fin Transmission Cooler, Black, 11 Inch: Automotive

This gives you the best of both worlds, it will let the trans get up to temp quickly (even in MN cold) and then stay @ the ideal range. the more cooling BTU capacity you can get the better off your going to be and the more control over the temp of the ATF your going to have. obviously space is always an issue so that is usually the limiting factor. + how much time and money you want to spend doing it.

there is really no debate about what works IMO. cooling capacity matters, and control over the temp range to circulate thru that capacity. pump flow rate is also a critical factor but your not going to swap that oil pump out. so you can control the other 2 factors.

https://www.toyota-4runner.org/3297726-post145.html

 

[vegask]

I've ran it both ways. I had my hayden 678 in series for close to a decade then switched it to bypass when I swapped the radiator out.

With the bypass, you really need to let your truck warm up in the winter before driving it. My transmission does not like to shift when its cold for the first mile or two of driving. Fall/Summer/Spring time there are zero issues.

For me, letting my runner warm up in the driveway for 5 or 10 minutes is no big deal as I only drive it a few times a week. And not risking pink milkshake is worth it to me. YMMV.

 

[Sarki]

When I bought my 02 4TR it had 180K miles. It was a single owner with extensive docs indicating dealer service but was still running original factory radiator.
I’m in NY where winter temps drop down below freezing on regular basis, sometimes in the teens. I also see summer temps in the 90’s, traffic, etc.
I replaced the original radiator with a Denso unit and installed the smaller B&M trans cooler in series with the new radiator.
As per Scangauge I’m now seeing cold trans temps (95-125) during the winter months even after warm up, as in during 2 hour highway drives.
During the winter trans temps have never gone above 130 after extended driving.
I know this can’t be good for the trans, not sure what the answer is but wanted OP to be aware of this situation as I imagine he deals with cold winter temps as well.

 

[Endlessblockades]

As long as you have a new radiator either way is fine as long as you are actually monitoring temps. I had a brand new radiator but I freaked myself out with a reading of 249 degrees hard climbing in heat so I added smallish stacked-plate Tru-Cool in series because that was better option to plumb for my setup and the hose I had. I also popped in a Magnefine filter at the same time. I cannot get the trans to top 200 degrees now under the same conditions. It runs at 150-160 on the highway now and I'm more worried about under-heating tranny oil when I warm the engine up now (it's always something). Also I need to add some more TF because I've added to the systems capacity with everything plus a loop of hose to place the filter where i wanted it. These systems do have odd spikes and drops for no apparent reason....

 

[3bears]

i ran bypassed when I lived in the lower 48. After moving here , about mid-way into my first winter I went back to in series to keep trans temps warmer. I use the torque pro app and do watch my temps. I beleive overheating your trans is bad, but I have also read running too cool is not good either. I run full synthetic in all the boxes and engine .
My new to me 4runner, will get a new radiator installed ( sitting on shelf) and a magnafine filter...but I wont be going with an extranl cooler.
so I think it really depends on your location and how you use it.

 

[HiluxSurf SSR-G]

how many in this forum who properly maintained the cooling system has experienced the pink milkshake?


just wanted to know if the pink milkshake has something to do with a poorly maintained cooling system. reason is that i read somewhere that the coolant becomes acidic or corrosive if it is not replaced regularly in accordance with the coolant manufacturer's recommendations.

 

[19963.4lsr5]

how many in this forum who properly maintained the cooling system has experienced the pink milkshake?


just wanted to know if the pink milkshake has something to do with a poorly maintained cooling system. reason is that i read somewhere that the coolant becomes acidic or corrosive if it is not replaced regularly in accordance with the coolant manufacturer's recommendations.

I almost had it.

Since I had just gotten the 97 Limited Puppy Hauler (it has its own thread) I was doing a routine of dumping the trans fluid every two weeks or so. One of those times I had milky streaks in the atf in the drain pan.

So I got a True-Cool 4589 and bypassed the factory Rad. It’s big and I had to relocate the horns.

A few years later I put head gaskets on it with fresh heads and installed a new rad. I pulled the old one apart and there are aluminum adapters that thread onto the internal cooler and seal to the lower plastic rad tank. The aluminum was just starting to corrode and allow antifreeze past the threads and into the ATF.


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[Romeo1]

Some interesting thoughts for sure. I’ll hook up the blue driver next time I’m out with it to see the temps are. Maybe if I can talk the wife into holding the laptop I’ll run a full data log with my AutoEnginuity setup to plot out temps at various points in the drive cycle. If guys are hitting 250+ the oil isn’t going to live long that’s for sure. That’s pretty dang hot though. You can usually smell or feel what’s going on by that point in my experience (with other vehicles).

Just out of curiosity, are you guys that are seeing high temps, are you just letting the transmission govern itself entirely when your seeing temperatures in the 250+ range? Because sure, if your floating between torque converter lockup and the never ending up down up down shift cycle in a load situation I could see were heat could be an issue. But why not just utilize the proper gear, OD lockout, ECT mode or 4lo for the given situation? It’s an “automatic” obviously, but there’s nothing wrong with driving it manually as needed.

Another thought is the guys that are having temp issues, are you running a plate bumper with less air flow through the cooling stack? Big tires on stick gears?

I still of the opinion that assuming the system is in proper working order and not full of trash and bugs, and geared accordingly, I’m not sure extra cooling is needed. These 3rd gens all seem to have a pile of miles on them, mine included, with so little issues it’s not even funny. Course, I went though the E4OD, 4R100, 47RE diesel truck days so it’s all relative…. Man that was a joke. Transmissions every 5 minutes it seemed like.

But to be fair I haven’t actually monitored the transmission temp, so I will test my sample of one out and report back. I push my rig pretty hard though. I treat it like a side by side with air conditioning from the moment it leaves the house. She gets drove though, no trailer queens here.