Can a transmission cooler be too large?

[Johnny248]

How do you know when an aux trans cooler is too small, just the right size, or too large (if that is even a thing).

Would it be stupid or overkill to replace a factory 5 row, 10" x 3ish" with a 32 row 13" x 11" ?

 

[edyvw]

How do you know when an aux trans cooler is too small, just the right size, or too large (if that is even a thing).

Would it be stupid or overkill to replace a factory 5 row, 10" x 3ish" with a 32 row 13" x 11" ?

If you don't have issues, maybe.
WHat is temperature?

 

[Nessism1]

Adding a bigger cooler will increase pressure loss in the system, which is never good. The OEM's know what they are doing, for the most part, so as long as you are staying within the towing capacity rating of the vehicle, there should be no reason to increase the radiator size.

 

[Johnny248]

If you don't have issues, maybe.
WHat is temperature?

Quick background. 3rd Gen Tacoma. They have some sort of trans cooler/warmer with thermostat and coolant running through it. It then runs to the radiator. Up until sometime in MY21, they also had an auxiliary transmission cooler which ran in line after the radiator, through a small air cooler in front of the radiator. That was deleted from the standard tow package. A lot of guys on the Taco forms swear by adding an aux cooler either to replace (if yours had one) , add on to, or just add (if your truck doesn't have one). Someone of the units they are adding are pretty large, and some even have auxiliary cooling fans mounted to them. I'm just wondering if that is really necessary if your truck already has the small auxiliary cooler?

 

[4wd]

Quick background. 3rd Gen Tacoma. They have some sort of trans cooler/warmer with thermostat and coolant running through it. It then runs to the radiator. Up until sometime in MY21, they also had an auxiliary transmission cooler which ran in line after the radiator, through a small air cooler in front of the radiator. That was deleted from the standard tow package. A lot of guys on the Taco forms swear by adding an aux cooler either to replace (if yours had one) , add on to, or just add (if your truck doesn't have one). Someone of the units they are adding are pretty large, and some even have auxiliary cooling fans mounted to them. I'm just wondering if that is really necessary if your truck already has the small auxiliary cooler?

TruCool LPD (low pressure drop) - would allow for a moderate sized cooler with very little system loss. It bypasses thicker ATF until hot …
(By internal design - no valves) …

 

[GRUMPYDUDE2]

If current trans temps run 180f or less in summer heat, live with what you have. Bigger will serve no useful benefit.
There really is no min temp for trans temps. If you ran 120f in winter, you would be fine. I have never seen a "too big" trans cooler.

 

[Johnny248]

B

If current trans temps run 180f or less in summer heat, live with what you have. Bigger will serve no useful benefit.
There really is no min temp for trans temps. If you ran 120f in winter, you would be fine. I have never seen a "too big" a cooler.

My questioning of being too large goes to the idea that transmissions doesn't generally shift as well or smooth when they are cold. They seem to start working better as they warm up to operating temperature. If you have a giant cooler than is dropping temps by 50° , could that cause shifting issues?

 

[GRUMPYDUDE2]

Syn fluids do away with most cold temp shift problems, They are thinner when cold, yet as thick non syn when hot.

My questioning of being too large goes to the idea that transmissions doesn't generally shift as well or smooth when they are cold. They seem to start working better as they warm up to operating temperature. If you have a giant cooler than is dropping temps by 50° , could that cause shifting issues?

 

[4wd]

B

My questioning of being too large goes to the idea that transmissions doesn't generally shift as well or smooth when they are cold. They seem to start working better as they warm up to operating temperature. If you have a giant cooler than is dropping temps by 50° , could that cause shifting issues?

Unless you went extreme - doubt you’ll knock off 50°
More like 20-40° …
You want to check for dimensions (space) too. They need to be spaced tight to the stack - where this is most important is moving slow and the radiator fans kick in. Too much gap and the air goes behind the cooler …

 

[thescreensavers]

Adding a bigger cooler will increase pressure loss in the system, which is never good.

Most transmissions cooler lines is just bypass flow (low pressure) and returns back to the trans pan. It wouldn't really make a difference.

OEMs need to eeak out all the MPG they can out of a vehicle and run the transmission hotter on thinner fluids these days.

imo it's why we are seeing more valvebody issues these days.

My GX460 is known to throw valvebody codes in as low at 100k miles. I have installed a cooler and a Magnefine filter which will extend its life considerably. Fluid temps are generally 30F cooler which also thickens up the fluid a bit which will protect the VB even more, win-win.

 

[The_Jeff]

Transmissions generally have a thermostat and let "enough" fluid go to the cooler. The only concerns I would have about a big cooler are mechanical, like being a target for rock damage or splicing the lines poorly. Coolers are optimistically rated, they say "good for towing 15k lbs" when they mean half that.

 

[clinebarger]

Most transmissions cooler lines is just bypass flow (low pressure) and returns back to the trans pan. It wouldn't really make a difference.

OEMs need to eeak out all the MPG they can out of a vehicle and run the transmission hotter on thinner fluids these days.

imo it's why we are seeing more valvebody issues these days.

My GX460 is known to throw valvebody codes in as low at 100k miles. I have installed a cooler and a Magnefine filter which will extend its life considerably. Fluid temps are generally 30F cooler which also thickens up the fluid a bit which will protect the VB even more, win-win.

Most transmissions use the cooler return for lubrication, Sometimes the entire geartrian, Sometimes a portion of the geartrian. It's very critical to not restrict cooler flow to much....The reason low pressure drop coolers exist.

 

[D60]

This was discussed deep into the video on the Tundra engines, specifically the deletion in '19 on the Tundra.

It was suggested this was mostly cost cutting and CAFE as hotter fluid can -- at least on paper -- require less effort to pump and thus you can claim improved MPG

The guy says most modern frictions are at risk of de-lam much above 240F and reportedly the units without coolers can see as high as 240F, so it's right on the edge.

 

[edyvw]

This was discussed deep into the video on the Tundra engines, specifically the deletion in '19 on the Tundra.

It was suggested this was mostly cost cutting and CAFE as hotter fluid can -- at least on paper -- require less effort to pump and thus you can claim improved MPG

The guy says most modern frictions are at risk of de-lam much above 240F and reportedly the units without coolers can see as high as 240F, so it's right on the edge.

On my Seqoia, that has heat exchanger instead of radiator cooler it fallows coolant temperature. Which means in regular operations 210-225f.
I am contemplating going radiator from older versions mostly bcs. once baby is 2-3yrs old we will do some off roading high in the mountains, and cooling might be an issue.

 

[Marcozi]

To answer the question: yes, a cooler can be too big. Why? Transmission are designed to perform optimally when the transmission is within a specific operating temperature range.

 

[altaylar]

B

My questioning of being too large goes to the idea that transmissions doesn't generally shift as well or smooth when they are cold. They seem to start working better as they warm up to operating temperature. If you have a giant cooler than is dropping temps by 50° , could that cause shifting issues?

Good point. I dont know if truck owners change transmission oil grade based on their use case, but some of us run thicker transmission oil in our cars that we track compared to what OEM spesificies. And those thicker transmission oil definitely hinders shifting feel when cold

 

[drtyler]

On my Seqoia, that has heat exchanger instead of radiator cooler it fallows coolant temperature. Which means in regular operations 210-225f.
I am contemplating going radiator from older versions mostly bcs. once baby is 2-3yrs old we will do some off roading high in the mountains, and cooling might be an issue.

@edyvw Not sure if you have seen this, but this bracket has been made for Tundra and Sequoia that lack the factory transmission cooler. About $115, but you have to buy the Hayden 689 cooler and the Toyota ATF thermostat and lines.

https://www.tundras.com/threads/transmission-cooler-bracket-kit-hayden-679-689.153340/

The factory cooler worked fine, but it's not the easiest to retrofit since the AC condenser is replaced with the combo ATF Cooler/AC condenser.

 

[edyvw]

@edyvw Not sure if you have seen this, but this bracket has been made for Tundra and Sequoia that lack the factory transmission cooler. About $115, but you have to buy the Hayden 689 cooler and the Toyota ATF thermostat and lines.

https://www.tundras.com/threads/transmission-cooler-bracket-kit-hayden-679-689.153340/

The factory cooler worked fine, but it's not the easiest to retrofit since the AC condenser is replaced with the combo ATF Cooler/AC condenser.

Hey,

Did not see that one. There is one that goes for like $1127 with 15 row Setrab cooler, all lines, thermostat etc.
Won’t do that yet as with new baby I am not going anywhere too far when it comes to off roading.

 

[drtyler]

Hey,

Did not see that one. There is one that goes for like $1127 with 15 row Setrab cooler, all lines, thermostat etc.
Won’t do that yet as with new baby I am not going anywhere too far when it comes to off roading.

Yes, that is a good kit. I think the Setrab is the better oil cooler for sure. They stay out of stock a lot, and I think that is why others came up with the Hayden 689 bracket.

 

[edyvw]

Yes, that is a good kit. I think the Setrab is the better oil cooler for sure. They stay out of stock a lot, and I think that is why others came up with the Hayden 689.

Yeah, I will probably buy it and slowly start figuring out. No rush. But, I don’t like that transmission temperature.