Torque Converter Temps on tracks

[RPP Senior Member Find all posts View Profile Close RPP]

Just came back from a jolly in the North Flinders Ranges SA. I have a 2018 GXL Prado with a couple of Scangauges daisy chained. I can see most ATF temps all the time now.

I noticed situations during which the temperature of the Torque Converter would rise to nearly 120 DegreesC. It normally sits in the 85-95 C range.

When driving up Mt Caernarvon (a couple of hours from the Park gate to the mountain top at 950m altitude, in 4L and with centre diff locked when grinding up the scores of steep shaley slopes) the Torque Converter temp sits in the nominal range.

But when cruising on very easy but windy, undulating gravel roads in 4H, the Torque Converter temp blows out to 110-120 C.

It seems to me that the ECU is too confused to engage the Torque Converter lockup, and therefore the oil starts to cook.

And I'm wondering what the safe operating temp range is.

Anybody else seeing this?

[Guest Close Guest]

Fitting of a torque converter lockup, (Stocklock or similar) will reduce temps on tracks/sand.

[ferktm Lurker Find all posts View Profile Close ferktm]

I have ordered the Richardsauto's one. Will fit it soon and tell.

have also installed an atf cooler... Temps were too much for the oil! Now they usually goes between 60 and 80º C.

[Aquanaught Lurker Find all posts View Profile Close Aquanaught]

Slightly off topic with respect to transmission temperatures with track usage but: On a recent loop from Melbourne via Simpson Desert and back towing a trailer I has some time to watch transmission and torque converter temperatures with respect to gear usage. I was a little disappointed and frustrated with the auto performance while towing (MY18 GXL).

Not surprisingly while towing in 5th gear (auto mode) with the torque converter unlocked the TC temps were 105 to 120 degrees, while driving in 4th made for a noisier run with increased fuel usage (~17.5l/100km) albeit with lower TC temperatures consequent on the TC being locked.

On the way back from the desert I played around a little and found that when towing in 5th (auto mode) and the TC temperature rose to the max value (~126 degrees from memory) for a short while the car would then of itself automatically lock the TC in 5th and naturally the TC temperature would drop accordingly. When this occurred I found that with just a little bit of effort by feathering the load pedal I could maintain TC lock while in 5th for quite some period of time even if it unlocked briefly every now and then. This unique state of driving nirvana with improved fuel economy, reduced engine noise and dropping transmission temperature was very evident.

If I came to a hill or had to overtake another vehicle and the auto dropped down to 4th or was unlocked in 5th long enough, the car's willingness to maintain the nirvana state of 5th gear lock evaporated. The only way to get back to this euphoric state of driving bliss was to allow the TC temperature to ramp back up to the maximum (~126 degree), after which the car decided to it was a good time to go through this whole process again.

In summary, the car would appear clever enough to lock in 5th gear to limit TC temperatures, and would appear also to think that ~126 degrees is an acceptable upper limit. If only we could reprogram to bring this threshold TC temp value down to something more reasonable...any takers???

I enquired of Toyota re putting in a transmission fluid cooler, but they say it will negate the transmission warranty. Without a Scangauge or similar the driver would not be aware of overly hot transmission temperatures, and presumably Toyota would rather the transmission run hot!

I have previously also installed my own TC lock up in a Pajero, but the car was out of warranty at the time. Maybe the TC lockup kit is the lesser of two warranty evils?

Thoughts welcome.

[ferktm Lurker Find all posts View Profile Close ferktm]

IMHO 126 C is too much for ATF!! And also IMHO if you have problems with the gearbox and uninstall the mods they won't know it!

i would love to talk to a Toyota engineer who can't lie and ask him about those transmission temps . Sometimes I do not know if we are doing it ok with tranny mods.

[Aquanaught Lurker Find all posts View Profile Close Aquanaught]

I agree with you ferktm. From memory when the TC temp reached ~126 degrees, the transmission fluid temp (ATF) reached ~116 degrees. Either way you look at it these temperatures appear too hot and would cause premature fluid breakdown and require more frequent fluid change out.

Based on Toyota argument that the "additional load on the fluid pump" associated with an additional oil cooler would void the warranty, I can only presume they favour overheating of the fluid (and perhaps more regular replacement) to additional pump loads.

My feeling is that the additional pump load would be small to insignificant, but it is what Toyota thinks or what can be proved in regard to the cause of any transmission problem that matters in the event of a claim for a transmission problem. Toyota's advice would probably be to "tow in 4th", which is probably fine for short distances but not great at all for long runs and touring.

Two and a half years to cooler install and counting....

[Prone Member Find all posts View Profile Close Prone]

Hi Aquanaught,

I have just completed ~13,000 K in 2 1/2 months towing a camper trailer behind my MY18 VX, Melbourne to Gulf to Broome to Alice Springs back to Melbourne and like you played with various gear arrangements.

Most of the trip I used S4 but at times when on the black stuff tried S5 and even S6.

I never found the 126 deg behaviour though as I have installed a transmission cooler. The highest temp I get now in normal use is about 105. Normally sits around 85ish while towing in S4. I had a previous model 3 litre 5 speed and it had noticeably lower temps even before I installed a cooler on it. The 6 speed seems to be 10 to 20 degrees hotter on similar roads to what I remember from the old car.

If the terrain was pretty flat and no head wind I found that I could use S5 and could get the torque converter (TC) to lock. However it was speed sensitive, much harder to lock when 95 plus than it was if I was travelling less than 95KPH. At times I could also travel with the TC locked in S6 as long as not above 95KPH. These are the indicated not true speeds which are about 3 to 4KPH less than true speed according to my GPS.

In the old 3 Litre 5 speed there was little difference in fuel consumption between S4 and S5 however this does not seem to be the case with the 2.8L 6 Speed. I think there is a noticeable fuel use increase when using S4 rather than S5, no definite figures but appears so on dash display. The engine noise is less in S5 and much less noisy in S6.

Cheers
Prone

[Aquanaught Lurker Find all posts View Profile Close Aquanaught]

Prone, envious of your 2.5 month trip. I was on a 2 week school holiday restriction. Notwithstanding the frustration and annoyance of the hot fluid temps the Prado went well and is so far proving comfortable, capable and reliable. Agree regarding improved noise and fuel economy going from S4 to S5 with the 2.8l 6sp auto when towing, a rough estimation is subjectively perhaps around 1.5l/100km improvement. I don't have experience with the 3.0l to compare to though.

Feedback in regard the long term effect of using a lock-up kit on the transmission longevity from what I can see is limited and subjective at best, so while I have installed one in a previous vehicle I am more inclined to put a cooler in than the lock-up kit to keep temperatures down. An installed cooler would be very evident to Toyota should I have a transmission warranty issue, although the catch 22 is that if I put in a cooler it will probably reduce chance of a warranty issue and extend the transmission life in the long run which has to be a good thing.

In the fulness of time once out of warranty I will probably get both.

My research has come up with the GENII and the Stocklock kits. The GENII appears to be just an on/off unit while the Stocklock appears to have the advantage of a speed sensitive mode which from my experience would be a useful additional functionality. Happy to hear feedback on these or any other lock-up kits.

[RPP Senior Member Find all posts View Profile Close RPP]

The key reason why Toyota (and thus their local outlets) don't like third party accessories (during the warranty period) is that the all-seeing ECU mostly doesn't know about them.
Anything that modifies the performance of the vehicle and/or is outside the visibility of the myriad of sensors feeding the ECU can baffle the software's pre-programmed understanding of whats going on.

Being an Engineer I see their point, especially with post fuel filters, lockup kits, re-mapping etc. However it doesn't help anyone that Toyota (and other makers) keep the behavior of their ECU software, and their specific OBD codes, a big secret.

On the plus side Toyota does occasionally come to the party with useful stuff like their Driving Light wiring harness, accommodating an auxiliary battery etc. And I do like the Prado.

The computer (ECU) control system is very complex, and peril sensitive, just read today's Australian about the family of 6 that got stuck on a dune in the Simpson (in a Patrol) when their engine stopped because of a failed sensor.

Complexity is the enemy of reliability, that's why Ive got 2 Scangauges displaying 8 readings, and might get another one, just so I can see whats going on and adjust my driving before things self destruct. BTW the readings I monitor are mostly Toyota specific OBD codes that are only available due to the R&D of members on the Pradopoint and Fortuner forums.

I have a tyre pressure monitoring system (an Ebay cheapie). It proved its worth last week in the Flinders when we pulled up to Wilpena and I noticed one tyre well down with a slow leak.
As opposed to last year in the Kimberley where I scored 3 flats in one day and must have driven at least 50Km on 2.5 tyres before I pulled over.

I too would like a Torque Converter manual Lockup kit, but I have a lease car and will wait 2.25 more years, and just keep and eye on the gauges in the meantime.

[krypto Avid PP Poster! Find all posts View Profile Close krypto]

The oil cooler has no effect on the ECU and has a significant impact on transmission oil temps, improving longevity of both the oil and the gearbox and improving transmission performance. Waiting until the warranty is up to install a cooler will reduce the long term life of the gearbox, especially if you do lots of towing and 4WD work. I fitted one as soon as I bought the Prado and never had any queries from Toyota during servicing and for a number of minor warranty issues.

[Aquanaught Lurker Find all posts View Profile Close Aquanaught]

RPP, understood in regard to vehicle ECU's and the complexity of the sensor network and feedback loops required particularly to achieve target emissions. Long gone are the days of clever but relatively simple and easily replaceable electro-mechanical engine controls.

As an engineer too, who spent 10 years developing engines for the likes of Ford, Land Rover, Honda and the like, albeit on the structural strength and fatigue side of things and not on the performance side, I appreciate the significant design and testing work put in to achieve a product that is reliable and meets the target specification for torque, power and emissions. For this reason I am particularly cautious of engine modifications that increase cylinder pressure or heat input and avoid such modes (there are probably some good modes out there that don't have any negative effect but I will live with the stock specification!). I can also appreciate the OEM's reluctance to open it all up to all comers to make modifications which may have significant consequence on engine and transmission longevity down the track. As long as they are providing a warranty I understand their desire to keep everything stock as their engineers designed and intended it to be.

I did not work on transmissions so am not across the full complexity of them and may be over simplifying things but when it comes to fluid temperatures I would thing that having cooler fluid (within reason) is better than >100 degrees temperatures, so doubt that there would be a down side to installing a transmission cooler (other than maybe the fluid pump longevity as indicated by the Toyota dealer when I asked!).

How good would it be if Toyota would provide an OEM transmission cooler for hotter climates such as here in Aus?

Where do you mount your Scangauges by the way? I had been contemplating using a bluetooth app to see more data but I like that the Scangauge just sits there out of the way and does not require touching a phone to operate it.

[Prone Member Find all posts View Profile Close Prone]

Toyota did provide an additional transmission cooler for the 5 speed Auto Petrol models but not the Diesels. It was in series with the cooling loop through the radiator. Not sure if it ever made it to the 6 speed transmission.

I have my Scangauge velcroed under the cooling/heating control buttons above the closeable compartment in the centre console.

Cheers
Prone

[RPP Senior Member Find all posts View Profile Close RPP]

I have Velcro'd them onto my dashmat. I run a flat Ethernet cable from the OBD cable via a straight-through Ethernet connector. The flat cable is easier to get up the side of the dash and hold down between velcro strips.
I use another short flat Ethernet cable (Ebay) to daisy-chain 2 Scangauges. They are a great headsup display.

The only problem with mounting the Scangauges on top of the dash is summer heat. I have to use a sun reflector when parking outside in the hot summer sun. The LCD screens malfunction when they get too hot and it takes 15mins of aircon to tease them back into life.

[Aquanaught Lurker Find all posts View Profile Close Aquanaught]

Thanks for the info feedback. I had tried locating mine in a few locations including on the centre console and on the dash but my eyes weren't up to it so have it closer on the steering column. The dash is probably the only place to locate two units, looks good.

I have convinced myself to get a transmission cooler to look after my transmission properly and will deal with any unlikely warranty arguments if and when they occur. Have ordered a kit so hope to get it installed before the end of year trip.

[ferktm Lurker Find all posts View Profile Close ferktm]

Talking about the torque converter lock up kit I Will install soon... I have never loved making mods to engine neither gearbox of a car but in this case, when the car knows ATF is too hot ,it locks the Tc

May TC lock activation in highway use reduce gearbox lifespan ?? What do you think ??