You're over thinking this big time. Do you even have a temp gauge on your trans? Post your numbers.

I never had an issue with the trans operating at less than 120° during sustained driving in any weather or any scenario; typically, even when it was -10° in CO, it would make it to 150° in a few miles. Typically it sits at 180° around town, only getting to ~230° on super long highway climb. And I'm using a much thicker and wider B&M cooler than the Hayden everyone else seems to use on here. My temp sensor is located in a spin on filter block right after the pump output, reading the fluid at its hottest point.

I don't know how you could over cool ATF, unless you had a radiator sized cooler. And I'll be damned if I went through the trouble of installing a massive cooler and routing -6 AN lines only to still have it inline with the garbage radiator "cooler". Defeats the purpose and adds unreliability.

 

I also have a B&M cooler and have driven in zero degree F conditions on the highway with no problems. The design of the B&M (and most well made coolers) take advantage of the temp/viscosity of ATF.

The way they do this when ATF is cooler and thicker it causes allot of resistance going through the small passages of the cooler rows. So they provide a carefully sized orifice that allows the ATF to bypass the cooler core.

As the ATF starts to heat up it gets thinner and instead of going around the core via the bypass orifice it passes through the core and is cooled down. If stars to get too cold it begins to thicken up and starts to go through the bypass orifice again.

Its a very simple system with no moving parts and is very reliable.

As far as the minimum ATF I did a good bit a research about this when I put my cooler in. ATF doesn't need to be heated up nearly as much as motor oil for several reasons. The main reason we heat up motor oil is to burn off all the moisture that gets in the oil from the blow-by of combustion. It also has a much wider viscosity range and was designed to have the optimal viscosity at 190+F because of the need to burn of the water from the combustion.

ATF on the other hand doesn't change nearly as much from 100F to 180F temp range. Because of this as long as your temp is at least 100F the ATF is able to do it job just fine.


One thing I would like to bring up that I think is important about coolers but often overlooked is distance from the condenser to the ATF cooler.

When I first mounted my cooler I suspended it by straps between the grill and the condenser and went for a drive in the sand at the beach. Quickly I noticed the ATF spiked hard and was 220F+ quick and even if I stopped and idled it wouldn't cool down.

Well as soon as I got on the road again even just going 35mph the temp dropped quick this told me it was a airflow issue. So when I got home I used one of my smokers I use to find leaks in A/C ductwork and could see the air going AROUND the cooler then into the condenser on the front of the 4runner.

So I used the zip ties and mounted the directly to the surface of the condenser and tried the smoker again. The results were a major difference and you could see smoke/air being pulled straight through the ATF cooler.

The results back at the beach showed the cooler was able to keep the ATF temp down much lower because of the improved airflow.

Just some food for thought when mounting your ATF cooler.

 

I would take the time to mount it solidly with a slight air gap (no more than 1/4") between the condenser and cooler. You don't want it connected to or rubbing against the condenser if you do any offroading. It'll rub a hole right through it over time, then you've got another pain in the ass problem to deal with.

 

is this just a problem with post 95 runners or should i be concerned with my 94 runner?

 

Potentially any radiator with a built-in tranny cooler has some inherent risk. Use the search functions...many threads around here on this topic.

 

There is no such thing as "over thinking" on Yotatech, we are 4runner fanatics and some people take the smallest things into serious consideration around here. Now to your points you made,

So 4Tard, do you live in Co or did you just drive through the -10 degree weather for a little bit and then right back into warmer weather?

You mentioned the lowest temps you get is 120 degrees on the hot side, i wonder how COLD the fluid is on the cool side entering the transmission (i'd wager well BELOW 100 degrees!!)

Sustaining below 100 degrees is not a temperature i'm OKAY with and you didn't provide any facts relating to ideal ATF temperatures so you cannot disprove what i'm saying.

During a cold start in 0 degree weather if i had BYPASSED my heat exchanger i would not be up to 100 degrees (hot side) by the time i start driving. I live right next to a highway so i'd be instantly driving at 60mph with no in town stop and go driving to get my tranny warmed up further. When driving in OD the tranny will never reach ideal temperatures. Most people that have temp gauges and/or scan gauges report ATF temps of +/- 70 on the hot side after about 10 minutes of idling. You cannot argue this, if so then you post your temps of start up and idle for ten minutes and then hit a highway at 60mph right away.

I have no solid proof nor do i have temp gauges. I however have read a ton of other peoples posts reporting their FACTS and RESULTS from a cooler bypass in FREEZING temps in these forums on YOTATECH. I don't have the time to cut and paste just to please your request of info. I did my research and formed my own opinion based on other peoples findings and if you want to risk it good for you but you shouldn't skew the results to make it appear your temps INSIDE your tranny are all peachy.

It's obvious that ATF is affected by temperature or else these oil coolers wouldn't come with BYPASS lines for cold ATF to directed to until the ATF heats up and runs through the cooler.

Some are facts and some are opinion, in my opinion for cold weather simply replacing the radiator with a new one gives me about 10 years of peace of mind at a small cost of $115.

 

just happened to me. waiting for results from shop. what did your $1100 consist of? was tranny salvageable? thanks. wish i seen website bfore this happened, i know what to do to prevent now, but after, not so sure.

 

Do a search here for strawberry milkshake and you'll find threads where transmissions were saved and what they did for flushing, etc.

 

thank you rworegon, yourself and others like you for helping me out.forums like yotatech and thier members have been very helpful. I stated before, wish i found site before this happened, oh well, live and learn. Thanks again

 

Does a radiator from a manual/5-spd have the internal trans cooler? If not, does anyone know if it's a drop in fit for automatic trans equipped 4runners? I know putting a bypass hose on isn't a big deal but I just thought that eliminating the internal cooler all together would be nice, and it would have a little more room for some extra coolant.

 

Here's what I know:

 

Pattycakes,
no, the radiator from a manual N185L (3rd gen 4WD) 4Runner doesn't have the ATF cooler inside its lower tank. however, the radiator is a bolt-on or drop-in fit on a A/T N185L 4Runner.

I am not sure though if the radiator from a N180L (3rd gen 2WD) 4Runner is bolt-on if used on an N185L 4Runner.

 

Anyone know the depth between the condenser and the vertical bar in the center of the rad that is behind the grill? I ordered a tru cool 4590 which is 11x11x1.5 and Im hoping if i need a small section to go underneath that bar then it will. Well crossing my fingers...

 

https://www.yotatech.com/members/pol...0&ref=gnr-next

I mounted the cooler behind the grill and plan on bypassing the rad cooler as this is, I believe, more or less, ineffective.

 

Expect to see a substantial increase in trans temps with your cooler mounted like that.

 

Buying an external cooler today. Where is the preferred mounting location? I was going to mount it flush to the AC condenser with some sponge tape between the two for vibration and wear resistance.

 

A couple things to note on minimum temperatures:

For the A340F (page 7 here in FSM: http://personal.utulsa.edu/~nathan-b...operatio.pdf):
"If any of the following conditions exist, the ECM turns off lock–up solenoid valve to disengage the lock–up clutch. [...]
4. The engine coolant temperature falls below 70C (158F). [...]
The purpose
of 4) is both to improve general driveability, and to speed up transmission warm–up."

What does this mean? Well as I understand it water to ATF fluid systems are designed to cool ATF fluid to the same temperature as your coolant. So 158* is the ideal operating temperature for your transmission as designed by the factory.

So since most external transmission coolers cool fluid to at least 30* beyond current, I see value in running the 180* thermostat bypass valve on all external transmission coolers in every climate -- and anytime you add a thermostat, it's a good idea to add a gauge to ensure your thermostat hasn't failed... (This is of course presuming that there is a reason for an automatic transmission to run at certain heat, beyond just ensuring that fluids are at a given viscosity -- can't answer that one, anyone else know?)

***Especially if you're running a synthetic ATF with higher viscosity across all temps (amsoil claims -60*F Pour Point), it's a good idea to run the temp bypass as the truflow's external cooler looks to be a mechanical/viscosity based system in which synthetic ATF w/ high viscosity would flow through all/most channels at standard above freezing temps -- or at least that's what I'm presuming...

IMPORTANT EDIT: FogRunner has a great thread advocating for lowest possible tran fluid temps if running synthetic atf, so disregard/don't use the thermostat bypass unless you absolutely need it due to cold climate: https://www.yotatech.com/forums/f2/t...esults-200965/

IMPORTANT EDIT 2: The more I research the more it seems that there's a reason for minimum tranny temps. Whether that's for maximum fluid viscosity or other reasons, I have not yet determined. But disregard the Important Edit above. Not sure I 100% agree w/ FogRunner on tranny temps as low as possible...

 

This site has a great write up as well with general/generic ATF fluid advice: http://www.digi-panel.com/trannyoil.htm

Automatic Transmissions

OIL TEMPERATURE MEASURED AT CONVERTER OUTLET TO COOLER:
300° F=
The maximum allowable temperature. This is the recommended place to install a temperature gauge or sensor. Do not allow the converter outlet temperature to exceed 300° F. The temperature at this location will vary significantly because of load, hill climbing, etceteras. If the temperature reaches 300° F, reduce throttle. To lower transmission temperature with transmission in neutral, run the engine at 1,200 RPM for at least 2 - 3 minutes while keeping a close check for signs of engine overheating. A transmission in a heavy throttle, stall condition (a typical situation is rocking a vehicle stuck in mud, sand, or snow), may increase temperature at a rate of 1° degree per second of stall.


OIL TEMPERATURE MEASURED AT OIL PAN OR SUMP:
150° F=
The minimum operating temperature. Note: It is possible in low ambient temperatures to overcool the transmission with auxiliary oil to air coolers. Oil to water coolers in standard factory radiators will normally not overcool a transmission.

175-200° F=
Normal pan oil temperature operating range.

275° F=
Maximum allowable oil pan temperature for short durations during long hill climbs.

300° F=
Damage occurs to internal transmission parts, including warpage of metal parts, degradation of clutches, and melting of seals. Transmission oil oxidizes, (forming varnish-like substances causing further clutch slippage and compounding heat build up) and transmission oil life is extremely short.


AUTOMATIC TRANSMISSION FLUID LIFE / TEMPERATURE RELATIONSHIP:

Automatic transmission oil can provide up to 100,000 miles of service before oxidation requires replacement, at an operating temperature of 175° F. Above this temperature, the oil oxidation rate doubles with each 20° degrees F increase in oil temperature. See chart.

ATF DEGREES F - MILES OF SERVICE
175 - 100,000
195 - 50,000
215 - 25,000
235 - 12,500
255 - 6,250
275 - 3,125
295 - 1,500
315 - 750
335 - 325
355 - 160
375 - 80
395 - 40


Note: Transmission oil and filter should always be changed more frequently when driving with heavy loads (RVs), typically at least every 25,000 mile intervals, since converter outlet temperatures then normally far exceed the ideal 175° F.

 

I also wanted to note that the factory towing package setup on the 93 3vze SR5 is:
1. tranny out line
2. to 3 pass plate and fin cooler (mounted away from condenser/radiator)
3. to radiator tranny cooling
4. back to tranny

Which also suggests that factory wants to keep the radiator fluid temperature above the 158* lock up temperature but below (yet closer to) the 180* engine operating temperature...

I'm going to keep looking into this, but it suggests some benefit to transmission operating in the 150-200 degree range rather the colder numbers some of you are posting and as FogRunner has posted elsewhere...

 

Here are the promised pics of the factory towing package's external tranny cooler.

As you can see, it's not the most effectively designed cooler, nor will it's placement allow it to have much effect except at highway speeds. And even then, a lot of air will go around rather than through.

Also, and again, the route of the cooling lines on factory is tranny to top of external cooler, out of bottom of tranny cooler to radiator tranny cooler and then from radiator tranny cooler back to transmission. This suggests that Toyota engineered it so that tranny fluid maintains a steady minimum temperature, which would be impossible to do if routing in reverse, from radiator to external cooler and then back to transmission.

From drivers side looking across:


Looking down:


And then looking at the connections:


I am still doing more research, but I am currently leaning more towards the need for a thermal bypass valve all the time if running just the auxillary cooler than not. But more research to come.

Any new insights from the boards?