Tranny Cooler: Bypass or In-Series

[19963.4lsr5]

Romeo1 my 47rh has 190,000 on it and still chirps the tires in the 1-2 upshift WOT.

Flashing the torque converter is the only heat source in an automatic. Locked it will run cold and unlocked temp wise the sky is the limit. I’ve driven home on a hot summer day many times on my 32mile drive and temp gunned my oil pan and read 130f.

I care more about what the temp of the ATF is in the oil pan over what the temp is coming out of the trans cause it’s gonna be hot if you’re working it unlocked under load.


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[Hopeless Diamond]

I put a temp gauge in the output to the cooler, so coming straight out of the torque converter I believe, should be the hottest temps in the system. I do run it in series to try and moderate the temps of the fluid in the trans itself. Many times in the winter/spring hwy driving, the gauge is barely reading anything at all, 90 or less (gauge will only read over 80). Having that radiator (new) in the system will keep the fluid temps up closer to a preferred operating temp. I do baby it offroad and am usually running in 4Lo to keep the temps down (usually ~25-30 degrees lower), sucks in the fuel though.

 

[phattyduck]

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.

Couple notes...

The factory trans fluid sensor is on the outlet of the trans - so it is the hottest fluid temp that the trans fluid sees. If you are used to 'pan' temps, they will be hotter than you are used to. That is also why there is a near immediate (maybe 10-20 seconds?) drop of ~20*F whenever the torque converter locks up at speed.

Also note that the A340 only locks the converter in top gear (4th for OD on, 3rd for OD off). So, at low speeds, not mater what manual shifting you do, it can't really help trans temps. 4LO really helps though, since it reduces torque load on the trans/torque converter by so much.

I have a new(ish) radiator, so I have my trans cooler plumbed in series with the stock radiator cooler. I also have a thermostat on there, plumbed to bypass both the OEM cooler and aftermarket cooler. Trans temps warm up fairly quick (haven't tried below freezing yet) and stay in the 170-200*F range almost exclusively. Higher end when torque converter is unlocked and lower end when unlocked.

-Charlie

 

[4runnerfiend]

Fluid control thermostat

Ran my bypass with in line fluid control thermostat. stays closed until 180 degrees and then opens up. works for me most of the time my temps are in the 175-190. I've seen up to 215-220 ish but as soon as you let off the tras cooler brings the temp down fast.
I've had mine on for a year and a half and no issues

You want the Tras temps in the optimal range too cold is not good for it.


Amazon.com: Derale 25792 Fluid Control Thermostat Kit: Automotive

 

[Fiffa]

Boy, this forum sure knows how to send me into a rabbit hole of research...

This thread had me concerned that my OBDII temp through the Torque app that are usually between 130-150F is hurting my nearly 300k mile transmission. Just found this quote from Jeffrey Diamond:

"In general, there is no danger of over-cooling the fluid"

Performance modifications for the Supra and Toyota A340E Automatic Transmission

I'm tempted to get either a 160 or 185 thermostat, but I'm curious just how bad consistent lower temps are?

 

[19963.4lsr5]

My local trans shop stopped putting those thermostats on because of the failure rate they had with them.

So I’ve never used them.


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[phattyduck]

I'm tempted to get either a 160 or 185 thermostat, but I'm curious just how bad consistent lower temps are?

If you keep up on fluid changes (normal factory schedule, maybe every 30k, right?) I wouldn't worry about it. As long as it is shifting normally for you, that is - that would be the only real possible issue with over cooling.

Warmer fluid will be better for efficiency, which may or may not be an issue for you. (I like the idea of efficiency, so that was part of my decision process, even if it never actually pay off)

-Charlie

 

[gamefreakgc]

Boy, this forum sure knows how to send me into a rabbit hole of research...

This thread had me concerned that my OBDII temp through the Torque app that are usually between 130-150F is hurting my nearly 300k mile transmission. Just found this quote from Jeffrey Diamond:

"In general, there is no danger of over-cooling the fluid"

Performance modifications for the Supra and Toyota A340E Automatic Transmission

I'm tempted to get either a 160 or 185 thermostat, but I'm curious just how bad consistent lower temps are?

The 160 won't help as much as you think. I have a 170 in mine and it heats up right past 170 and into the 190's low 200's in the summer. All it means is that it opens sooner, doesn't actually increase the cooling capacity. It will mean you will run colder in the winter though. I hardly ever touch over 170 in the winter which means my heater doesn't work as good as others.

If you keep up on fluid changes (normal factory schedule, maybe every 30k, right?) I wouldn't worry about it. As long as it is shifting normally for you, that is - that would be the only real possible issue with over cooling.

Warmer fluid will be better for efficiency, which may or may not be an issue for you. (I like the idea of efficiency, so that was part of my decision process, even if it never actually pay off)

-Charlie

Ha, maybe we'll get a 2% increase in fuel mileage! From 17 to 17.34 MPG! I was hoping the same thing when switching to full synthetic everything and, drum roll please, noticed no change. Oh well.

 

[phattyduck]

Ha, maybe we'll get a 2% increase in fuel mileage! From 17 to 17.34 MPG! I was hoping the same thing when switching to full synthetic everything and, drum roll please, noticed no change. Oh well.

Well, I do have a log of every gas fill up and maintenance/mod on the truck for the last >300k miles, so... :bounce:

(it used to get 24-26mpg regularly when it was younger and 2WD, now it is more like 20mpg)

-Charlie

 

[OrRunner]

I ran mine in series and am glad I did. I wheel in Oregon and it's a lot of tight, hilly, low speed runs. With a new radiator and fresh fluids I was seeing 260 at times. Even with the cooler in series I see up to 230 or so at times. For that kind of work I'd definitely recommend doing it in serious... it also will warm the fluid in cold weather. Best of both worlds.

 

[PlutosT4r]

Having gone through the milkshake, it blows my mind this is even a debate. Yes, you should absolutely buy a new radiator... and bypass it.

 

[Endlessblockades]

The answer to this question is always 'Yes' when you have a fresh radiator. Your choice.


Edit - since I have been running a Tru-cool in series for a year and have a 1.5 year old radiator, I think I'm going to plumb it to bypass and see what the temp change is on my UltraGauge, if any.

 

[phattyduck]

Having gone through the milkshake, it blows my mind this is even a debate. Yes, you should absolutely buy a new radiator... and bypass it.

Or, you know, take care of your truck. I replaced my (original!) radiator around 2017/8 around 270k miles. I took apart the bottom tank and cooler - 0 corrosion present. Funny thing - when you keep up on your fluid changes (rad and trans), you don't get internal corrosion that leads to the pink milkshake.

I now have a big enough secondary trans cooler (with thermostat) so I probably don't need to use the radiator cooler anymore - but maybe using it for power steering instead might be helpful.

-Charlie

 

[jgue467]

I added external cooler in series before and after my new radiator.

I found out without it, in stop-go Austin May-Oct 100+ weather while towing, the radiator alone would not keep trans below 200 (sometimes would hit 215) so back on the internal radiator circuit and voila, well under 200 at all times now.

As others said, just keep the toyota red fresh. Your cooling may vary.

 

[19963.4lsr5]

Or, you know, take care of your truck. I replaced my (original!) radiator around 2017/8 around 270k miles. I took apart the bottom tank and cooler - 0 corrosion present. Funny thing - when you keep up on your fluid changes (rad and trans), you don't get internal corrosion that leads to the pink milkshake.

I now have a big enough secondary trans cooler (with thermostat) so I probably don't need to use the radiator cooler anymore - but maybe using it for power steering instead might be helpful.

-Charlie

Every three years I drain the Rad and top it off. Keeps it fresh and I don’t have to deal with draining the block and potential air pockets…


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[PlutosT4r]

My mistake was "taking care of the truck". I thought I wouldn't need a bypass, being the outstanding citizen I was. Though, the rig was being pushed hard. So maybe it is my fault for not bypassing sooner.

Now, I think even a stock grocery rig needs a bypass. I would not want to think, "it's only those guys that need to bypass, I'm fine". I think this is one of those things that you just have to experience, it will magically change one's logic. Mine was well taken care of. Many people take care of their rides and still get the milkshake. Two year old radiator. Can't blame all the owners.... Maybe some.

 

[PlutosT4r]

Every three years I drain the Rad and top it off. Keeps it fresh and I don’t have to deal with draining the block and potential air pockets…


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Every 3 years? That seems like a long time... I guess if you sample the fluid out the bottom and it looks clean, no problem.

 

[jgue467]

Every 3 years? That seems like a long time...

My 01 schedule says coolant drain every 120 Months, I try to remember at 60.

The toyota red coolant does say good for 'Life' or 150K.

 

[19963.4lsr5]

My 01 schedule says coolant drain every 120 Months, I try to remember at 60.

The toyota red coolant does say good for 'Life' or 150K.

Yep most stuff is at minim 5 year coolant.


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[cl4Rk]

I added external cooler in series before and after my new radiator.

I found out without it, in stop-go Austin May-Oct 100+ weather while towing, the radiator alone would not keep trans below 200 (sometimes would hit 215) so back on the internal radiator circuit and voila, well under 200 at all times now.

As others said, just keep the toyota red fresh. Your cooling may vary.

Are you running two external coolers?

Like:
Transmission —> first external cooler —> radiator —> second external cooler —> return to transmission