Transmission cooler opinions

DDeezenuts

DDeezenuts

New member
Good afternoon all,

I have a 2000 T4R limited 4x4. I installed a B&M 70264 transmission cooler (13,000-14,000 BTU) a few years ago. I pull a 1700lb camping trailer a few times a year. Unhooked from the trailer and on the highway with the trailer there are no issues with heat since there is airflow. However, the issue is when I am making long pulls uphill with or without the trailer my temps go up to 210-220* pretty quick. They do come down but some passes in the mountains can be for miles of uphill travel. Just want to take care of my investment and prolong life of transmission. I now have a scanguage to monitor trans temp btw. Here are some of my thoughts on remedies and questions...

I am considering the following tru-cool transmission coolers: LPD4921 (34,000 BTU - 6" x 23" x .75"), H7B (29,200 BTU - 11" x 11" x 1.5"), LPD4590 (28,000 BTU - 11" x 11" x 1.5"), or LPD4589 (24,000 BTU - 11" x 11" x 1.5").

Any thoughts on how large to go? Largest? Middle sized and add fan for slow speed uphill pulls?

FWIW, 95% of my miles are with no trailer and no mountain roads. I live in Ft Worth, Texas so its relatively flat but can be pretty hot. 90-100* in summer but occasionally, I will travel out west where it is just as hot and there are long uphill grades (some slow and some high speed). Its the long, slow uphill pulls that worry me.
 
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DDeezenuts said:
However, the issue is when I am making long pulls uphill with or without the trailer my temps go up to 210-220* pretty quick. They do come down but some passes in the mountains can be for miles of uphill travel. Just want to take care of my investment and prolong life of transmission. I now have a scanguage to monitor trans temp btw. Here are some of my thoughts on remedies and questions...
Click to expand...
First, what speeds are you talking about and are you turning off overdrive to keep the torque converter locked as much as possible?

Second... the OBD-II reported temperature is the HOTTEST the fluid ever is. It is on the outlet to the cooler, before it returns to the trans (after going through the hydraulic pump and torque converter if unlocked). You can rest a bit easier knowing the average temp of the fluid in your trans is (much) cooler than your reading.

I might be in the minority on here, but 210-220*F while working the truck hard every once in a while isn't much of a problem. The factory idiot/warning light on the dash turns on up near 300*F... As long as the average overall temps are good and you keep up on semi-regular fluid changes, you'll have no problems running as you have it now.

-Charlie
 
good questions and I should have specified...

On the uphill pulls, the ECT is on and overdrive is off. In fact, ECT is on and overdrive is off most of the time when pulling the trailer now. On long, flat pulls on the highway, I will turn the OD back on to drop the RPMs somewhat. In regards to speed, under 30-40MPH (when going uphill with trailer) seems to not generate enough air flow and result in higher temps. Above 40 seems to be ok.

Good to know on the trans temps. I have read that the scan guage is higher than actual but some people say its close to actual so not sure what to believe unless I actually install a dedicated gauge which I do not really want to do at the moment.

If you were going to change the cooler which would you suggest? My AT oil temp light came on recently (before I had the scangauge). I was going uphill for about 30 minutes at 20 mph. OD was on and I can not remember if the ECT was on/off. I immediately shut the car off and let it cool. It scared me so I bought the scangauge.

I am significantly more cognizant to keep the OD off and ECT on while pulling the trailer now. Planning on changing the fluid, transmission filter, and adding magnafine inline filter ASAP.
 
I too do not think that 220 is bad at all.

The 4589 is what I installed in the puppy hauler. It’s the biggest I think will fit without some relocating of things.


Sent from my iPhone using Tapatalk
 
ECT makes no difference in temps, it only adjust shift points so yes it can help with acceleration but that is it.

OD override makes a tremendous difference, i use it going uphills only, with or without towing, drops into 3rd locked, so no slipping and cools tranny down nicely.

Careful if you get a really large external cooler, get one that closes itself off if the temps are low like in winter.

You may want to double check the radiator cap is good, go OEM toyota.

I would also check the fan clutch, it may be old enough it needs replacing.

Luck.
 
Turning overdrive off will only help you at speeds of about 40 mph or greater. It allows for the torque converter to lock up in 3rd gear which keeps the fluid cooler. If you aren't in 3rd gear with the torque converter locked up then it's not going to matter.

If you are looking to upsize I used a tru-cool 4589 which is rated for 21k BTU. I bypassed the radiator cooler as well and haven't had any issues from doing so.
 
Bad Luck said:
Turning overdrive off will only help you at speeds of about 40 mph or greater. It allows for the torque converter to lock up in 3rd gear which keeps the fluid cooler. If you aren't in 3rd gear with the torque converter locked up then it's not going to matter.

If you are looking to upsize I used a tru-cool 4589 which is rated for 21k BTU. I bypassed the radiator cooler as well and haven't had any issues from doing so.
Click to expand...

I also have that same one, the Tru-Cool 4589. I rarely tow but my supercharger puts out a ton of heat and stress on the transmission. The previous owner fried the transmission because of the extra heat and put a rebuild one in, which is the one I'm currently using. I have had no burnt fluid or premature coolant degradation since putting it in.

It does have a cold fluid bypass of sorts but the installation manual does say to put it inline with the radiator if you live in a cold climate that sees below freezing temperatures on a regular basis (basically if you live in snow) because the fluid will be too thick to properly lubricate the transmission components.

Since you are looking for just occasional towing useage, that would be my suggestion. I would install it in-line with the stock radiator cooler but having it in series after the radiator. So flow would go from transmission -> stock radiator cooler -> external cooler -> transmission feed line, if that makes sense. That way you are protected in towing/hot weather as well as cold.
 
gamefreakgc said:
I also have that same one, the Tru-Cool 4589. I rarely tow but my supercharger puts out a ton of heat and stress on the transmission. The previous owner fried the transmission because of the extra heat and put a rebuild one in, which is the one I'm currently using. I have had no burnt fluid or premature coolant degradation since putting it in.

It does have a cold fluid bypass of sorts but the installation manual does say to put it inline with the radiator if you live in a cold climate that sees below freezing temperatures on a regular basis (basically if you live in snow) because the fluid will be too thick to properly lubricate the transmission components.

Since you are looking for just occasional towing useage, that would be my suggestion. I would install it in-line with the stock radiator cooler but having it in series after the radiator. So flow would go from transmission -> stock radiator cooler -> external cooler -> transmission feed line, if that makes sense. That way you are protected in towing/hot weather as well as cold.
Click to expand...

Knowing that I bypassed my stock radiator does that change your thoughts at all?
 
Bad Luck said:
Turning overdrive off will only help you at speeds of about 40 mph or greater. It allows for the torque converter to lock up in 3rd gear which keeps the fluid cooler. If you aren't in 3rd gear with the torque converter locked up then it's not going to matter.

If you are looking to upsize I used a tru-cool 4589 which is rated for 21k BTU. I bypassed the radiator cooler as well and haven't had any issues from doing so.
Click to expand...

how does the tranny cooler do in low speed, hi torque situations?
 
DDeezenuts said:
how does the tranny cooler do in low speed, hi torque situations?
Click to expand...
I haven't towed anything substantial or driven in conditions similar to what you are describing. I live in the Ozarks foothills so there aren't any sustained grades in my area. Sorry I can't be of more help bud
 
Spend the money on a new rad and use the internal trans cooler in series with your current trans cooler.

If you still don’t like your trans temps then go for the 4589. That plus the trans cooler in the rad should be all you’ll need.

Rather than spending the money on the cooler I’d spend that money on a new rad which will include a cooler you can use.


Sent from my iPhone using Tapatalk
 
DDeezenuts said:
good questions and I should have specified...

On the uphill pulls, the ECT is on and overdrive is off. In fact, ECT is on and overdrive is off most of the time when pulling the trailer now. On long, flat pulls on the highway, I will turn the OD back on to drop the RPMs somewhat. In regards to speed, under 30-40MPH (when going uphill with trailer) seems to not generate enough air flow and result in higher temps. Above 40 seems to be ok.
Click to expand...
This clears it up right here. It isn't an airflow issue. In 3rd gear (OD off), the torque converter locks up somewhere in the 40-45mph range. Below that, it is unlocked (it never locks in 1st or 2nd). The unlocked torque converter is what is creating all your heat, not the lack of airflow.

You won't experience the warning light again, but the best way to cool the trans (stated in the owners manual, I believe) is to idle in park, not stop the engine. You need the trans fluid to continue to circulate through the trans to cool it.

-Charlie
 
Too much throttle will unlock the torque converter above its lockup mph.

If you keep the RPMs above the stall speed of the torque converter it will keep the temp spikes to a minimum.


Sent from my iPhone using Tapatalk
 
phattyduck said:
This clears it up right here. It isn't an airflow issue. In 3rd gear (OD off), the torque converter locks up somewhere in the 40-45mph range. Below that, it is unlocked (it never locks in 1st or 2nd). The unlocked torque converter is what is creating all your heat, not the lack of airflow.

You won't experience the warning light again, but the best way to cool the trans (stated in the owners manual, I believe) is to idle in park, not stop the engine. You need the trans fluid to continue to circulate through the trans to cool it.

-Charlie
Click to expand...

Does the torque converter/transmission not move transmission fluid through the cooler in 1st or 2nd gear?
 
DDeezenuts said:
Does the torque converter/transmission not move transmission fluid through the cooler in 1st or 2nd gear?
Click to expand...

It does, as long as the engine is turning and therefore turning the torque converter, the fluid is moving as the torque converter is what is linked to the transmission oil pump. When the torque converter is unlocked (meaning it's spinning faster than the engine) it creates more heat than when it is locked, where it spins 1:1 with the engine RPM. It cannot lock in 1st or 2nd.
 
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