Trans Temps with Bypassing and Using External Cooler

[mtbtim]

Ok, I know there have been some heated debates regarding if it's advisable to bypass your OEM internal transmission cooler in the radiator and use a stand-alone external one to avoid the "Pink Milkshake". I read through quite a bit of the thread [MENTION=78997]Drcoffee[/MENTION] started and other related threads but I still would like some more data.

For those that have bypassed the radiator cooler and also are using a Scan Gauge or other monitoring system, what temperatures are you registering? What I'm mainly looking for is the environmental / mechanical extremes. I want to know the temps people are registering while wheeling in extreme heat, like in the dessert. I also want to know the temps on the opposite side of the spectrum where you're operating in very cold climates. The icing on the cake is if anyone actually has recorded the temps in the extremes while using the OEM radiator cooler and compared it with the stand-alone cooler in the extremes as well.

I would love to have the piece of mind that I'll never have to worry about contaminating my trans fluid with radiator coolant and destroy my transmission, but at the same time, I wouldn't want this modification to potentially shorten the life of my transmission by having it operate in the very high or the very low temperature ranges. The reason is I do visit very very hot locations going mountain biking in high dessert regions and I also visit cold regions like Tahoe in the winter.

I am of the opinion that the chances of a radiator cooler failure is probably very slim, but why not have 100% guarantee of not having this sort of failure by bypassing and using an external cooler IF a stand-alone cooler will do the job as effectively as the OEM radiator cooler set-up.

 

[A.Wilson013]

I have an AEM Trans temp gauge installed right between my external cooler and transmission. My thought was that this would be the warmest point, as it's just before it goes into the cooler.

The highest temp I have ever seen was on a hot day (PNW hot... It was like 85) in LOOSE sand with all 4 wheels spinning as I sluggishly pulled a Ford Expedition that was buried to the frame. The temp read 245 degrees.

Cruising around town I hang out around 120 unless it's a hot day (80+) when I'll see 150-175.

Wheeling in the summer I usually stay in the high 100s to low 200s.

This is all with the little guy B&M 70268

 

[SnowLizard]

I know I don't have a cooler installed (yet) but my temps have been roughly 160-195 on street driving, 100+ heat. (higher if something is wrong, like tiggle valve position)

wheeling in heat, I'm roughly 200* can peak to 210, but I try to be nice. I've been watching the temp, I have a brand new radiator. my plan is add the cooler inline with the radiator (after I'm told is best, but honestly want to try it both ways and see the temp differences)

My summer heat will easily be 110+, and being 'dry' air it will take more air to get it to cool.

 

[nihkon]

I have the B&M 70264 cooler installed and bypassed oem cooler. Via the scangauge, my normal around-town temps range from 150-185. On a recent wheeling trip, it averaged 250, and skyrocketed to 290 at a particularly strenuous section! This was up a somewhat steep fire road, and fairly low speeds......meaning no airflow over the aftermarket cooler.

I just recently purchased a pusher fan to install on the aftermarket cooler to try to help with the lack of airflow at low speeds. I'll probably wire it so that it comes on automatically based on temperature, but also wire in a switch to that I can manually flip it on for wheeling.

 

[A.Wilson013]

I have the B&M 70264 cooler installed and bypassed oem cooler. Via the scangauge, my normal around-town temps range from 150-185. On a recent wheeling trip, it averaged 250, and skyrocketed to 290 at a particularly strenuous section! This was up a somewhat steep fire road, and fairly low speeds......meaning no airflow over the aftermarket cooler.

I just recently purchased a pusher fan to install on the aftermarket cooler to try to help with the lack of airflow at low speeds. I'll probably wire it so that it comes on automatically based on temperature, but also wire in a switch to that I can manually flip it on for wheeling.

For what it's worth, my Scan Gauge reads right around 10 degrees warmer than my AEM gauge when in what I would consider the operating range (110-170ish). When it's under 110, the gap is closer, around 5 degrees, and over 170 it starts to get larger, 15 or so degrees.

 

[jgue467]

With the toyo design the upper limit of the trans temp is the engine coolant temp so about 195.

With the bypass the limit is beyond that. In my case it has to be 'summer' (which in central texas is from may thru oct) around 100+ and climbing significant hills or mountain passes (west texas Davis, Sierras - either).

Without doing anything but climbing mine (bypassed) can reach 238, within 8-15 seconds of activating the OD override the temps drop to 198 or less. So this 230+ situation is EZ to avoid plus OD also helps ease the strain of the climb on these smallish V6s. I drain/fill with full synthetic every spring and change the magnefine filter too.

In the winter (around 30 here) once 30 minutes of driving is elapsed it'll hit 160 tops. I am happy I did the bypass, just adds a little bit of manual effort on big climbs on hot summer days. :hippie:

 

[mtbtim]

Bump. Thanks to those who have replied so far. Anyone else got some data to share?

 

[poleclimber63]

More data..

Well, I've been running a tranny cooler bypassing the rad for 4 years now-- with a temp gauge mounted in the same location as A.Wilson013. After some reading, I determined the ideal median operating temp is 160. Every season I do a fluid change with synthetic fluid.
The first couple of years I ran a single cooler (a B+M 70268) which I wasn't totally happy with. During cold weather operation it took 20-30min to register 110 on the gauge and during heavy loads, the highest temp I observed was 180. During hot weather driving, temps varied from 140-220, quite a wide range. However, Under heavy loads ie. towing my 3200lbs sportboat, or climbing hard with a full load, I witnessed temps 250! Not great. So when I did an engine replacement in 14', I placed a second cooler with a thermo bypass. Under cold weather operation, there's been no noticeable change in temps, however, during hot weather, temps vary from 140 -180, a much more consistence range. During heavy loads ie towing, I've never seen it beyond 210, and usually not more than 200. As I tow a lot in the Summer and really make my truck work, I've become totally comfortable with how my setup performs.

 

[mtbtim]

Pretty good response so far. Got some good temperature data from people who are running bypassed systems in different weather and driving conditions. It would be cool to see some more temperature data from people using the stock radiator cooler in different conditions.

 

[St Runner]

My 97 ran from 170 at the lowest to 220 at the highest when I had the auto. Too high for my liking but my driving conditions are completely different than 99% of the members on here. Alway under 40 mph on steep and twisty roads where the torque convertor does not get to lock up. I will note that when I bought the vehicle the transmission fluid was black so the radiator cooling was not doing a much better job. My advise is that BEFORE you put in a separate cooler have something to measure the temperature. Buy a scanguage, it is well worth it and if you have an 96-98 get a separate gauge. Good information leads to good decisions, guessing leads to poor decisions. As a side note I was watching Jay Leno's garage and one of his 1920's cars had about 20 gauges including a brake pressure gauge!

 

[Bstrom]

A definite pattern here - haulers and crawlers have more issue with temps than us roadrunners would. That second cooler scheme above is smart and cheaper to keep your tranny intact.

I'm adding the B&M cooler to mine after looking at the parts for 4 months and am glad to see it will work just fine for my needs. Gonna look for a thermostat to keep the fluid warm in winter - that should offset the original radiator function concept.

On my '99 I've read that the Scangauge (or Ultragauge?) will disable ABS if I use it - something weird like that. Anybody know if the '99s can get tranny temps without issue from either of these gauges?

 

[mtbtim]

So far, we're seeing a pattern that bypassed systems can record very high trans temps when the truck is used under conditions like towing and wheeling in high heat. And, it looks like a way to address this is to add an electric fan to pull more air over the cooler or maybe just add a second cooler.

Anybody else have numbers for the OEM setup in more extreme conditions/situations - towing in the mountains and high heat, wheeling in high heat, etc?

 

[Drcoffee]

With the toyo design the upper limit of the trans temp is the engine coolant temp so about 195.

With the bypass the limit is beyond that. In my case it has to be 'summer' (which in central texas is from may thru oct) around 100+ and climbing significant hills or mountain passes (west texas Davis, Sierras - either).

Without doing anything but climbing mine (bypassed) can reach 238, within 8-15 seconds of activating the OD override the temps drop to 198 or less. So this 230+ situation is EZ to avoid plus OD also helps ease the strain of the climb on these smallish V6s. I drain/fill with full synthetic every spring and change the magnefine filter too.

In the winter (around 30 here) once 30 minutes of driving is elapsed it'll hit 160 tops. I am happy I did the bypass, just adds a little bit of manual effort on big climbs on hot summer days. :hippie:

So, thats the rub. If you are not running it like a manual, you risk COOKING your tranny. If you are routinely going above 200* you will shorten the life of the ATF and the ATF is the lifesblood of the transmission. The simple truth is this. If you undersize the cooler you will burn up your tranny. If you oversize the cooler, you run too cold and will also damage the tranny.

Just so we are all clear. You DE-ACTIVATED the OD, not activated it. Pushing the button turns off the 5th gear and make the TC lock up.

I run mine in series with the radiator. I run 125* in winter and 180* in summer. Techically in the designed operating temperature range. If you are concerned about the milkshake , buy a new radiator. For pete's sake, they cost $70 at rockauto.com. What is that? Two frickin pizzas. For you west coasters its probably two nickel bags of weed.

 

[BlazeRunner]

I noticed nobody talks much about the placement of the coolers, which will greatly affect how the airflow passes through the cooler, thus affecting the temperature readings. Improper placement can quickly kill airflow.

 

[mtbtim]

So, thats the rub. If you are not running it like a manual, you risk COOKING your tranny. If you are routinely going above 200* you will shorten the life of the ATF and the ATF is the lifesblood of the transmission. The simple truth is this. If you undersize the cooler you will burn up your tranny. If you oversize the cooler, you run too cold and will also damage the tranny.

Just so we are all clear. You DE-ACTIVATED the OD, not activated it. Pushing the button turns off the 5th gear and make the TC lock up.

I run mine in series with the radiator. I run 125* in winter and 180* in summer. Techically in the designed operating temperature range. If you are concerned about the milkshake , buy a new radiator. For pete's sake, they cost $70 at rockauto.com. What is that? Two frickin pizzas. For you west coasters its probably two nickel bags of weed.

[MENTION=78997]Drcoffee[/MENTION], I remember you stating you replaced your radiator with a Koyo brand. As I understand it, Koyo at one time made the OEM radiators for Toyota and that's why they have been recommended. However, how does one know the quality of the ones Koyo is selling now is on par with the ones they were making for Toyota at one time? I was thinking when I replace my radiator, I was just going to go with an OEM one from Camelback but the price is closer to $200. There was one member, [MENTION=70753]badattitude[/MENTION] who stated he has looked at a few different radiators and the OEM was the best built model he's seen. Here's what he said on the the thread "Koyo vs The Rest".

I bought a denso radiator from amazon 9 months ago. I expected to be same as a OEM Toyota radiator. It was not as good and arrived with a broken off by-pass nipple. In particular the rubber mounts on the OEM Toyota were not on the the aftermarket Denso and overall quality was not same as the Toyota radiator. I returned the broken Denso and bought a genuine Toyota radiator. If it didn't have the broken by-pass nipple I would have just gone ahead and used it. My point is, Denso makes the Toyota Radiator but the Denso's sold online are not the same as the ones in a Toyota box.

Correction, it is NipponDenso that makes the Toyota radiator. Thanks T4R2014

I think Koyo is better than Denso but Toyota Branded Denso is best. I've had all three. I like to buy from Amazon (Im a prime member) although Toyota of Dallas and Grapevine Toyota have good prices to. They come with rubber plugs over the tans ports but they would need a zip tie or something to hold them on better.

Do you think this $70 radiator is truly on par with an OEM one?

 

[Drcoffee]

You know, if you can afford an OEM then go that route. If you are driving a 16 year old truck with the original OEM radiator, then I would say this. A new aftermarket radiator is better than a corroded OEM radiator. So buy what you can afford. Most guys here are complaining about the cost of a radiator when the extra coolers, hose, and fancy fans and bypasses are going to cost well over $300. Most people wont own the truck long enough to wear out the aftermarket radiator. So does it really matter? If the internal ATF cooler is going to fail, guess what? The radiator will fail and the coolant will pour out. So it doesn't go into the tranny, but it will still leave you stranded. What fails in the old radiator is the mount of the internal cooler to the lower tank of the radiator. It vibrates and once corroded, snaps off breaking the seal.

So a lesser quality aftermarket radiator is SUPERIOR to the old worn out OEM. Yes it is on par with an old OEM, no it is not on par with the new OEM.

 

[amalik]

[MENTION=78997]Drcoffee[/MENTION], the bypass school of thought isn't saying a new radiator is too expensive. They are saying they don't want to run the risk of the ATF and coolant ever mixing, even if it's a new radiator.

Myself as an example, I have a aux tranny cooler (I think TruCool or something, it's not B&M), and also bought a new radiator at the same time.

I've been contemplating switching over to in-series though.

 

[StreetCreeper]

... For pete's sake, they cost $70 at rockauto.com. What is that? Two frickin pizzas. For you west coasters its probably two nickel bags of weed.

$70 will get you a 1/4 oz of the good stuff. Or maybe an 1/8th and some Round Table pizza...and a sack of Funyuns.

 

[badattitude]

A $70 is not as good as a $200 Toyota radiator but any new radiator is better than one with 150,000 miles and 15 years on it. The radiator is a unique part on these trucks. Owners can't be too careful with radiators due to the corrotion issue. IMO it's just as important to use Toyota red coolant. Toyota parts are usually the best. I want to say always the best. It's so much easier to get wholesale prices now. I liked the Koyo radiator but like having a Toyota one even better.

 

[MountainBiker]

Anybody else have numbers for the OEM setup in more extreme conditions/situations - towing in the mountains and high heat, wheeling in high heat, etc?

- ~5 year old aftermarket radiator put in by the PO
-no external trans cooler
-Scangauge just installed last month
= 255 peak trans temp climbing a long dirt road in 1st and 2nd gear low range (I saw a lot of 220-240 temps on this climb, the 255 was the peak, all at 60 degree air temperature.) So I'll be adding an external cooler very soon!

It's worth noting that driving in low range increased the engine RPM to around 3k for this whole climb, which speeds up the water pump, and more importantly, increases the fan speed significantly. And based on how the engine responds, this RPM must be very close to the torque converter stall speed.

FWIW, I can easily see >220 temp on the freeway on a grade (not towing, but with a load of camping gear), in either 3rd or 4th gear (there is no 5th gear, as someone implied earlier.) In all of these situations discussed in this post, the engine coolant temp was reading 195-200 on the Scangauge.