Transmission Temperatures and How it Relates to Life of the Fluid

[chasingmagiclight]

I usually keep OD on unless I'm going up a steady climb on the highway, driving on mountain roads or going down a grade and I want a little engine braking. I may be wrong, but since having the OD on lowers the rpms, your gas mileage will be better.

In my testing OD is the main factor in high transmission temp! I just added a trans temperature gauge (my year does NOT have one) and after my last trip my conclusion is I have been driving my 4runner incorrectly for the last 18 years! Similar to you I would only disable OD for big hills. My recent observation is that OD significantly increases the trans temperature on anything but very flat or downhill sections. My new habit is no OD except on downhill sections and my temp peaks at around 150F (previous behavior would routinely get 200F plus) My mileage was no worse than normal (16mpg with full load and RTT)

 

[mtbtim]

In my testing OD is the main factor in high transmission temp! I just added a trans temperature gauge (my year does NOT have one) and after my last trip my conclusion is I have been driving my 4runner incorrectly for the last 18 years! Similar to you I would only disable OD for big hills. My recent observation is that OD significantly increases the trans temperature on anything but very flat or downhill sections. My new habit is no OD except on downhill sections and my temp peaks at around 150F (previous behavior would routinely get 200F plus) My mileage was no worse than normal (16mpg with full load and RTT)

Trans fluid is at an optimum temperature around 180 degrees. A good range is 150-180 but even temps in the low 200's isn't horrible. It's when you're pushing above 230 you have to start worrying. At 230 degrees, trans fluid can last around 36,000 miles. If it reaches 250, that same fluid will only last around 10,000 miles. Too low of a temperature (below 150) for long periods isn't good for your transmission either because condensation can build up inside and supposedly isn't good for it.

So, you really want your trans fluid temps to be above 150 but below 230 to allow your fluid to last the normal life span of 30,000 miles. I remember reading in vehicle owners manuals that trans fluid should be renewed every 30,000 miles unless you're towing and then it's suggested every 15,000 miles. I'm guessing the 15,000 mile renewal suggestion is because they're assuming there's a chance you spiked your trans temp and the effective life of the fluid has been shortened.

 

[Kotrin]

Trans fluid is at an optimum temperature around 180 degrees. A good range is 150-180 but even temps in the low 200's isn't horrible. It's when you're pushing above 230 you have to start worrying. At 230 degrees, trans fluid can last around 36,000 miles. If it reaches 250, that same fluid will only last around 10,000 miles. Too low of a temperature (below 150) for long periods isn't good for your transmission either because condensation can build up inside and supposedly isn't good for it.

So, you really want your trans fluid temps to be above 150 but below 230 to allow your fluid to last the normal life span of 30,000 miles. I remember reading in vehicle owners manuals that trans fluid should be renewed every 30,000 miles unless you're towing and then it's suggested every 15,000 miles. I'm guessing the 15,000 mile renewal suggestion is because they're assuming there's a chance you spiked your trans temp and the effective life of the fluid has been shortened.

Yeah, the Toyota FSM says normal temperature of 122-176, but what I found interesting was further reading showed that you can test it between 68 and 230 for working correctly. To me this is telling me that 230 is okay, not OMG stop. What I thought was interesting is I read this page by page and I found that the Light was tied to 300F(I think). I completely understand and know from certain situations that oil breaks down faster with excessive heat. I feel better now that I my fluid has been changed and I'll do it every 10k most likley due to the temperatures I continuously see.

The interesting thing was the 300F for the light. To me, if I'm seeing those temperatures I'm already in trouble..

 

[mtbtim]

Yeah, the Toyota FSM says normal temperature of 122-176, but what I found interesting was further reading showed that you can test it between 68 and 230 for working correctly. To me this is telling me that 230 is okay, not OMG stop. What I thought was interesting is I read this page by page and I found that the Light was tied to 300F(I think). I completely understand and know from certain situations that oil breaks down faster with excessive heat. I feel better now that I my fluid has been changed and I'll do it every 10k most likley due to the temperatures I continuously see.

The interesting thing was the 300F for the light. To me, if I'm seeing those temperatures I'm already in trouble..

Yep, 230 is not horrible and many will see this high of a temp in their automatic transmission if they're driving up steep grades or towing without even knowing it since they're not monitoring the trans temp. But, I would say 230 is the point where I'd start watching it really closely if I was towing or climbing mountain roads loaded down with gear. Now with my external B&M 70264 cooler installed, the highest temp I've seen is around 205 degrees climbing the same hill I hit 232 on a previous trip.

That's interesting the idiot light is set at 300 degrees. At that temp, the fluid is completely toast. I guess that means stop and get your truck towed.

 

[AZPartsGuy]

On the highway, I'm running in the 130's, but if it's a longer drive, the temps finally make it into the mid to high 140's. Since I now know that trans temps below 150 isn't optimal, I'm wondering if adding the cooler was the best choice.

I see the same temps in the morning when I head to work and I still have the stock setup. This morning my trans was 91* when I started it and about 130* when I hit the freeway, ~160* by the time I parked. 8-ish miles to work in Phoenix, 4 of those on the freeway.

During my lunch break, though, it'll start around 120* and hit up to 195* by the time I park.

 

[DK327]

I've seen mine reach 199F during stop and go traffic in town but it's usually hovering at 160-180. I don't have my B&M installed yet and my thermostat is at 12pm position for 202-207F engine temp. I'm gonna take a 775 mile trip to KY tomorrow from NE and will keep an eye on temps and gas mileage going 65mph to see how they'll jump around... When I return, I'll probably redo the thermostat at 6pm and install the B&M trans cooler before going on another 600 mile trip to SD in July and see what kind of difference, if any, those changes made... Should be interesting...

 

[mtbtim]

I've seen mine reach 199F during stop and go traffic in town but it's usually hovering at 160-180. I don't have my B&M installed yet and my thermostat is at 12pm position for 202-207F engine temp. I'm gonna take a 775 mile trip to KY tomorrow from NE and will keep an eye on temps and gas mileage going 65mph to see how they'll jump around... When I return, I'll probably redo the thermostat at 6pm and install the B&M trans cooler before going on another 600 mile trip to SD in July and see what kind of difference, if any, those changes made... Should be interesting...

I'm starting to wonder if the jiggle valve position is crucial or not. On my truck, I recently replaced my thermostat and the jiggle valve was in the 3 o'clock position. I put the new one in the 6 o'clock position and there's no difference in the temperature. Still hovers around 190.

Doing some research on the thermostat jiggle valve, it's purpose is to let trapped air out of the system after you've drained and refilled your coolant. Once the air is out of the system, I wonder if the jiggle valve does anything further. Another recent member on the forum, [MENTION=115590]StreetCreeper[/MENTION], replaced his thermostat and he found his original thermostat jiggle valve in the 1 o'clock position. You would think since it's purpose is to let trapped air out, the 12 o'clock position would make the most sense since air rises.

However, people have reported that changing the jiggle valve does make a temperature difference. Why it makes a difference on some rigs and not others is a mystery. I'm sort of thinking people's rigs that are running a little hotter than normal may have more to do with the fan clutch getting tired.

 

[Kotrin]

Yep, 230 is not horrible and many will see this high of a temp in their automatic transmission if they're driving up steep grades or towing without even knowing it since they're not monitoring the trans temp. But, I would say 230 is the point where I'd start watching it really closely if I was towing or climbing mountain roads loaded down with gear. Now with my external B&M 70264 cooler installed, the highest temp I've seen is around 205 degrees climbing the same hill I hit 232 on a previous trip.

That's interesting the idiot light is set at 300 degrees. At that temp, the fluid is completely toast. I guess that means stop and get your truck towed.

So it was myself, my son a cooler of Beer(Caprisuns for my son) and 3 rc cars and going from 2,000' up to 5,000' I had OD not turned off and it climbed up to 230 with the B&M cooler. I leave for my trip here really soon and i'll be monitoring it closely as i'm curious how the temps will do. But I hear people switching to the B&M cooler and seeing huge improvements. I didn't have my SCGII till after I had done my cooler, so I wonder if my ran higher before hand(probably did). But what I see is I run average running around town like 180's easily. If i'm on a curvy road with hills, 200 no problem and close to 210-215. All these temps were BEFORE i changed the fluid. I will be taking the same road this Friday when I pick-up my son and I will keep an eye on it to see if its an improvement. I have noticed when switching to OD off it will drop my temps by 20 degree's even with ECT on and driving it like I'm racing =).

My son and I over the weekend were doing some trail exploring and I put it in to 2 and saw the temps drop way down even with it 90F outside. I really feel its a learn to balance and after 400 miles off-road i'll be a master =D

 

[DK327]

I leave for my trip here really soon and i'll be monitoring it closely as i'm curious how the temps will do

Looking forward to your results on Friday... As for me, I just got back from a 1500 mile round trip. Vehicle now has 233K miles on the clock and it performed excellent; there were no issues to report. My water temp remained around 204F and trans at 184F consistently... I hit rush hour traffic on the way back after having already traveled 8 hours and during those 15-20 mins of stop and go traffic, the trans actually reached 221F. Soon as we started moving again it quickly dropped to below 200 and stayed there. I averaged 20mpg @ 68mph with the AC blasting the entire way there and back.

 

[mtbtim]

So it was myself, my son a cooler of Beer(Caprisuns for my son) and 3 rc cars and going from 2,000' up to 5,000' I had OD not turned off and it climbed up to 230 with the B&M cooler. I leave for my trip here really soon and i'll be monitoring it closely as i'm curious how the temps will do. But I hear people switching to the B&M cooler and seeing huge improvements. I didn't have my SCGII till after I had done my cooler, so I wonder if my ran higher before hand(probably did). But what I see is I run average running around town like 180's easily. If i'm on a curvy road with hills, 200 no problem and close to 210-215. All these temps were BEFORE i changed the fluid. I will be taking the same road this Friday when I pick-up my son and I will keep an eye on it to see if its an improvement. I have noticed when switching to OD off it will drop my temps by 20 degree's even with ECT on and driving it like I'm racing =).

My son and I over the weekend were doing some trail exploring and I put it in to 2 and saw the temps drop way down even with it 90F outside. I really feel its a learn to balance and after 400 miles off-road i'll be a master =D

I can't remember if you mentioned it but how did you install your B&M cooler, meaning did you bypass the stock radiator cooler or did you run it in-series with the radiator cooler? Where did you mount the cooler? I mounted mine onto the AC condenser with the zip ties.

I have also noticed turning off OD makes a big difference in the trans temp so I always turn it off when I'm driving mountain roads or climbing a mountain pass on the highway.

Yep, if you're running your cooler in-series like me, you were probably running around 20 degrees hotter before the install so just think the temps you were hitting. You might have hit 250 before you knew the trick about turning off the OD and didn't have the external cooler. Supposedly, if you reached 250 degrees, your ATF will only last around 10,000 miles.

 

[mtbtim]

Looking forward to your results on Friday... As for me, I just got back from a 1500 mile round trip. Vehicle now has 233K miles on the clock and it performed excellent; there were no issues to report. My water temp remained around 204F and trans at 184F consistently... I hit rush hour traffic on the way back after having already traveled 8 hours and during those 15-20 mins of stop and go traffic, the trans actually reached 221F. Soon as we started moving again it quickly dropped to below 200 and stayed there. I averaged 20mpg @ 68mph with the AC blasting the entire way there and back.

When are you going to install your cooler?

 

[DK327]

When are you going to install your cooler?

I'm placing an order for a few QT's of Toyota trans fluid today to replace lost fluid when I take the hoses off and also to add more after adding the lines to compensate for fluid inside the lines and the external cooler as well as future trans fluid drain and refill... They'll probably arrive sometime next week so I'm shooting for next weekend. As for the thermostat, I already have the new gasket and a gallon of Toyota 50/50 coolant on hand so I'll do that at the same time. Will update once everything is done and I'm back from my SD trip, with my findings. I'll be happy with sub 200F temps on both engine and transmission.

 

[Kotrin]

I can't remember if you mentioned it but how did you install your B&M cooler, meaning did you bypass the stock radiator cooler or did you run it in-series with the radiator cooler? Where did you mount the cooler? I mounted mine onto the AC condenser with the zip ties.

I have also noticed turning off OD makes a big difference in the trans temp so I always turn it off when I'm driving mountain roads or climbing a mountain pass on the highway.

Yep, if you're running your cooler in-series like me, you were probably running around 20 degrees hotter before the install so just think the temps you were hitting. You might have hit 250 before you knew the trick about turning off the OD and didn't have the external cooler. Supposedly, if you reached 250 degrees, your ATF will only last around 10,000 miles.

Umm, in front of the others mounted using the BM cooler accessories through the radiators with the little zip thingies???. Bypassed the radiator completely due to pink milkshake and not wanting to replace the radiator at this time. I think the OD being off on hill climbs or slow, turns and such will make a GIANT difference.

 

[Kotrin]

Looking forward to your results on Friday... As for me, I just got back from a 1500 mile round trip. Vehicle now has 233K miles on the clock and it performed excellent; there were no issues to report. My water temp remained around 204F and trans at 184F consistently... I hit rush hour traffic on the way back after having already traveled 8 hours and during those 15-20 mins of stop and go traffic, the trans actually reached 221F. Soon as we started moving again it quickly dropped to below 200 and stayed there. I averaged 20mpg @ 68mph with the AC blasting the entire way there and back.

It was cooler by a lot with the OD off even at 3-4k rpm's doing 60. I will be leaving on Sunday for my trip and am looking forward to it one as i've been house locked for almost a year minus a few trips out. This is my first real trip over 80 miles to a location. First day is 270 miles to the beginning of the trail start and plan to do 30 miles of 370 on gravel/logging/snow/dirt/mud/etc roads that DAY. I will post my entire trip summary of elevation, speed, etc etc like I did last year on my trip. So I will do a trip of OD on and off for a control variable.

I'm so excited but its painful to load the vehicle. Why my co-pilot is in complete understanding of my limitations (he's gone with me before on different trips) and understands. One of the few people who understands my conditions and doesn't punish me like 99% of the others I run into in real life and on the internet.


So, can't wait!!

 

[mtbtim]

It was cooler by a lot with the OD off even at 3-4k rpm's doing 60. I will be leaving on Sunday for my trip and am looking forward to it one as i've been house locked for almost a year minus a few trips out. This is my first real trip over 80 miles to a location. First day is 270 miles to the beginning of the trail start and plan to do 30 miles of 370 on gravel/logging/snow/dirt/mud/etc roads that DAY. I will post my entire trip summary of elevation, speed, etc etc like I did last year on my trip. So I will do a trip of OD on and off for a control variable.

I'm so excited but its painful to load the vehicle. Why my co-pilot is in complete understanding of my limitations (he's gone with me before on different trips) and understands. One of the few people who understands my conditions and doesn't punish me like 99% of the others I run into in real life and on the internet.


So, can't wait!!

Definitely keep an eye on your trans temp when you hit a long extended grade. When I say extended, I'm talking 5 miles plus. The highest trans temp I've seen so far was climbing a long steep mountain road for probably around 10 miles. Another good test would probably be off-roading up some steep trails where you're going slow and won't have the benefit of air flow through your cooler.

Have a good trip!

 

[mtbtim]

So how many quarts are in a 4Runner? Are most people doing drain and fill or a "flush" when they trans fluid is changed?

From my research, our rigs hold around 12 quarts.

Whether to drain and refill or do a complete flush depends on the person. I've always done the drain and refill because it's easy and effective. But, I don't wait until 30,000 miles to do it since I know I'm only renewing around 5 quarts every time (around 40% of the capacity). I do a drain and refill every 10,000 miles. My fluid always looks clean and never smells burnt doing it this way.

 

[3bears]

an update for me and my truck
I have run with the radiator bypassed
I live in the mountains where we are already seeing 32 degree mornings

the other day, ( hot and after 2 hours of hiway driving) fully loaded on a back gravel steep road, I saw temps hit 231

from everything I have seen, I think this might be a cold winter ( where I am at). I don't want to run the tranny too cold

so I have ordered a new radiator (Denso), thermostat (Toyota), a new magnafine tranny filter, 16 qts of amsoil synthetic for a full flush,will pick up some condenser cleaner and go back to not bypassing the radiator

I dropped the pan and did a flush about a year ago added a magnafine and a B&M

What I did not know about my truck when I bought it... ( got all the papers after buying) is I suspect it had a pink milkshake, as about 6 years ago, at the Toyota dealer, it had a radiator replacement and a transmission service on the same day. With the customers comment of hard shifting. Its been about 60k since then.

so I don't want to push this tranny any harder , and I don't want to do damage to it by running toooo cold this winter.
If next summer when I hit my favorite mountain roads again I see those temps again, I will install a pusher fan on the B&M

I do have the cooler zip tied to the condenser so maybe not enough airflow, so I will mount it out away next spring/summer ( let it sit there now for the winter and be warm and fuzzy)

 

[ivopivo]

Is there any info on what the minimum temp should be for the trans fluid? I’m asking because all my life I went by the idea that fluid/oil should be “hot enough” to lubricate thigs properly. This is now something I’d like to know before I connect the trans cooler and possibly run “too cool”.

I have been tracking my temps with the autometer gauge (about 12-15” away from trans pan, in the hot/send line) and most around town stuff has peaked at 180-190 in the summer. I recently went to colorado for some offroading and there the trans got up to 220-230 for brief periods going up mountains etc. On the trails with low gears and o/d off it was again a consistent 170-200 even up 30-40* inclines on some passess.

Long story short, I’m having second thoughts about actually installing the cooler as I believe my trans would run probably 120-140 95-99% of the time. It would only help on some of the offroad or mountain roads that I would take few times yearly.

Thoughts?

 

[mtbtim]

Is there any info on what the minimum temp should be for the trans fluid? I’m asking because all my life I went by the idea that fluid/oil should be “hot enough” to lubricate thigs properly. This is now something I’d like to know before I connect the trans cooler and possibly run “too cool”.

I have been tracking my temps with the autometer gauge (about 12-15” away from trans pan, in the hot/send line) and most around town stuff has peaked at 180-190 in the summer. I recently went to colorado for some offroading and there the trans got up to 220-230 for brief periods going up mountains etc. On the trails with low gears and o/d off it was again a consistent 170-200 even up 30-40* inclines on some passess.

Long story short, I’m having second thoughts about actually installing the cooler as I believe my trans would run probably 120-140 95-99% of the time. It would only help on some of the offroad or mountain roads that I would take few times yearly.

Thoughts?

You bring up a valid concern about what the minimum temp should be. From my research, optimum ATF temps are around 170 F. The FSM says normal operating temp is 158-176. Even before I installed my external trans cooler, I would see temps in the 130's cruising down the highway on a mild temp day. The temperature your trans runs at depends on a lot of factors, ambient temp, speed of travel (air flow through the radiator and/or trans cooler cooling fins, strain on the trans (climbing grades), input from driver (turning OD off).

What most experts agree on is HEAT is the big killer of auto transmissions. Yes, having it run too cold all the time could allow moisture to build up in the trans and maybe the internal parts aren't lubricated as optimally at lower temps, but overheating your trans and not renewing the fluid on a regular basis are the real killers.

In regards to running too cold, external trans cooler manufacturers don't recommend bypassing the stock cooler in the radiator, especially if you live in cold climates because you lose some of the fluid heat transfer that happens with the trans cooler bathed in the hot engine coolant.

My B&M 70264 trans cooler allows my trans to run around 20 degrees cooler which can make a pretty big difference when you're climbing grades or towing. Since you're in Chicago with cold winters, your concern is legitimate. The coolers like mine have a low-temperature bypass that's suppose to divert the thicker fluid straight through cooler and not allow the fluid into the cooling fin channels until it thins out as it heats up.

 

[Drcoffee]

I just found some information on a website regarding transmission temperatures and how it relates to the life of the fluid. Normal driving will raise your temperatures to around 80 degrees celsius or 176 degree fahrenheit. At this temperature, the fluid could last you up to 100,000 miles. But, most transmissions will get hotter than this for various reasons (towing, driving up a steep 4x4 trail, etc.). For every 15 degree celsius above 80, the fluid's lifespan is cut in half. At 90 degrees celsius or 194 degrees fahrenheit, the fluid will last for 50,000 miles. At 110 celsius or 230 degrees fahrenheit which is commonly encountered in many transmissions, the fluid life is cut to 37,000 miles. I guess this is why it's suggested to change your ATF at 30,000 mile intervals. At 120 degree celsius or 250 degrees fahrenheit, the life of the fluid is cut to around 9300 miles.

The hottest I've seen my trans get is 232. That was from driving up a steep mountain road, carrying a bunch of gear and pulling a motorcycle trailer. I have since installed a B&M 70264 cooler in series with the radiator cooler and have seen a 20 degrees temperature drop. So, hopefully I won't be seeing anything much more than 210 in my rig now.

So, if you're regularly seeing temps above 230, you should either be doing something to get the temps down or changing your trans fluid much more often to extend the life of your transmission.

Here's the link to the website if you'd like to read more. I think you'll find it pretty interesting.
General Information - The Transmission Centre

Hi Tim,

I just installed a tru-cool 4544 11"x11"x.75" cooler on my FJ cruiser and it does a better job of cooling than the bm 70264 I have used on other vehicles. Higher rated as well. The FJC never sees above 150*F on the highway. Its flat enough to fit bewteen the vertical support and condenser. The 4544 has 3/8" ports and fin and plate design.

Ideally you want the ATF temp between 130*F and 170*F