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  • #16
    just had a thought - what if we switch in a resistor across the ATF temp sensor ( which would have to isolate the sensor at the same time ) to fool the ECU into thinking that the temp is 125deg ? instant , cheap lock up kit? lol
    Last edited by nudgebar; 28-11-2018, 04:57 PM. Reason: extra info

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    • #17
      Not sure what a resistor in parallel with the sensor would do.
      Assuming the sensor produces a voltage output, a high ohm resistor wouldn't do anything, and a low ohm resistor might overload the sensor.

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      • #18
        ive modified my post above to make it clearer . it would depend on the type of sensor of course. Temp sensors are usually just a 2 wire thermistor , so if you wanted the ECU to react or do something at a certain reading then you could substitute a resistor for the sensor.

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        • #19
          No worries.

          You would have to swat up on the specs of the thermistor in order to size up an appropriate resistor to put in series I'm thinking. The ECU would be applying a constant voltage and reading back the varying current. Maybe have the sum total present a 20degree C higher reading than the actual sensor's read. So that 105 become 125 and outlockup ensues.

          I'm toying with the concept of a heat exchanger tho. I've read some data on an available manual lockup kit. It is actually set up to lock and unlock at a couple of adjustable speed ranges.

          My scenario is not towing, but traveling in 4H over easy but undulating & windy gravel roads.
          I only recently added a second Scangauge to see more readings simultaneously and was surprised to see the Torque Converter temp go thu the roof on what was basically an easy road. At 120C, and over, the seals cant be happy.

          A couple of us are gearing up for a remote trek in the Kimberley mid next year and I want to get this sorted before then

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          • #20
            Transmission cooler is now installed along with peace of mind. No opportunity yet to see how it performs under tough conditions but will no doubt see the benefits when towing over the up coming holidays. Big Grin.

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            • #21
              Thanks Aquanaught,
              let me know how it performs. I'm tempted to have one installed also.
              I'm gearing up for a big long trek mid next year on a remote track in the tropics and need to get all upgrades sorted out by end of Q1 2019.

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              • #22
                Report back on the transmission cooler effectiveness. Not surprisingly quite an improvement.

                On road commuting with no trailer, the Transmission Pan typically runs 65 to 80 degrees, rough estimate probably around 15 degrees cooler than without the cooler. The Torque Converter runs typically between 0 and 10 degrees hotter depending on it being locked or unlocked.

                Hilly touring to the Hi Country, Transmission Pan temperature around 75 to 85 degrees.

                Off road low range, steep slow accents and decent in Hi Country, maximum Transmission pan temperature 86 degrees, with TC temperature no more than 97 degrees.

                Still haven't towed the trailer yet but will report back on this in a few weeks.


                Gary

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                • #23
                  Where is the heat exchanger mounted?

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                  • #24
                    Hi all,
                    I too am noticing the significantly higher temps on the transmission TC on normal hwy driving (IE Hume @110km/hr). Under those conditions my recollection is that the TC temp would climb to around 125C and the gearbox would change down a gear AND lock up. So I would see the RPM jump up and the TC temp slowly fall back down followed eventually by the gearbox shifting back up and the cycle would repeat. I find under most touring conditions (loaded with roofrack) I almost never see 6th gear spending nearly the whole time in 5th or 4th.

                    One thing I have noticed is that when travelling with one of my mates in a Fortuner his TC and Pan temps are significantly lower than mine in pretty much all conditions.
                    This is quite odd as the cars are very similar; both 2016, both lifted 50mm, both with ARB bullbar, both usually loaded to a similar extent when travelling together, both using the same PID decodes to read the temps.

                    There are however two possibly significant differences :-
                    1) I have the ARB underbody kit fitted to the Prado which replaced the standard unit which had a significant air vent in front of the transmission wheras the ARB underbody does not
                    2) The shroud below (but part of) his ARB bullbar fitment has additional vents wheras mine does not.

                    I'm wondering if the guys reporting high TC temps are all fitted with a bullbar and/or extra underbody protection? Anyone with the standard front end / no bullbar noticing high TC temps?

                    I only did a few thousand km before fitting the bullbar to the Prado and I dont remember it hunting between 4-5-6th on those first few trips but being a massive change from the Patrol I probably wouldnt have noticed anyway.

                    2016 Prado GX 2.8L Auto (The third tourer)
                    Y61 becomes Y62, R51 becomes R52. Nissan what are you smoking?
                    2013 Patrol GU 3.0L Auto (The second tourer)
                    2010 Patrol GU 3.0L Auto (The first tourer)
                    1991 Patrol GU 4.2 Auto (The training wheels)

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                    • #25
                      Hi ExNissan,
                      I have an ARB Bullbar on my 2018 GXL Prado and the Toyota standard underbody.
                      I have seen the TC Temp climb to 120C plus on what I thought was benign mildly undulating and winding gravel roads in the North Flinders ranges. Driving in 4Hi 40-60-80Km/hr.
                      At our destination we spent the next 5 hours in 4Lo, occasionally with the diff locked, grinding around the mountains with TC Temp nominal.

                      Recently on a bitumen highway thru undulating farmlands I saw the TC temp edge past 110C.
                      The next time this happens I will select S mode and constrain the gearing range just to see what happens.

                      I also can't tell what gear I'm in. How do you tell?

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                      • #26
                        Hi mate,
                        I notice this overtemp change down predominantly on hwy or sometimes very fast dirt. Under most driving conditions Dave's 'tuna is usually running a bit cooler than my Prado hence my interest in airflow differences. The difference between the two cars seems to be become significantly more pronounced the higher the speed.

                        As for what gear, I've got a GX so your setup may be different, if you put it into S6 and and drive it up to say 100km then change to S5 if the rpm changes it was in 6 otherwise 5th or below. Its a dodgy way to do it but it makes use of the fact that S mode is really just offering driver suggestions to the transmission control unit which it may chose to ignore. S6 is basically drive with possibly slightly more agressing shifting IMHO.

                        Once you do this a few times in the 80-110 speed range you will get a feel for 4,5,6 gear RPM's at a given speed. Flick it back to Auto and you should be able to make a pretty reliable questimate as to whats gear its in.
                        Lock up is easy to detect - if the TC is unlocked a slight throttle change will cause a change in rpm that isnt in sync with a change in road speed.

                        As an aside I've had a brief look into determing actual gear and lockup status via OBD but it didnt look to be immediatly obvious, If time permits I'll have a bit more of a look but my plate is pretty full right at the moment.
                        2016 Prado GX 2.8L Auto (The third tourer)
                        Y61 becomes Y62, R51 becomes R52. Nissan what are you smoking?
                        2013 Patrol GU 3.0L Auto (The second tourer)
                        2010 Patrol GU 3.0L Auto (The first tourer)
                        1991 Patrol GU 4.2 Auto (The training wheels)

                        Comment


                        • #27
                          Report back on the transmission cooler effectiveness when towing. Towed Melbourne to Orbost and back over the last week at the speed limit of 100 km/h and some bits at 110km/h.


                          The transmission temps typically ranged from 85 on the flat to 95 degrees on the hills, with the TC temperature as per the transmission temps when the TC was locked, but getting over 95 to 105 degrees with the TC unlocked, with peaks of around 112 degrees on longer hills. The TC runs typically up to 17 degrees hotter than the transmission when unlocked for a while and pulling hard.

                          The transmission was more likely to be locked in 4th than 5th, but but did not lock-up in 4th very often when really needed.

                          While the transmission temperatures are now much better with the cooler than previously, the peak TC temps are still too hot for my liking as the TC remains unlocked a fair proportion of the time when towing hard, so am now contemplating a lock-up kit for towing.

                          For the record regarding airflow, I have an ARB bulbar and full under body protection.

                          Last edited by Aquanaught; 10-01-2019, 09:56 PM.

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                          • #28
                            I cannot understand why Toyota allows the auto trans to drop out of lockup and not select 4th gear lock up. Of course temps will rise as the vehicle is being driven by the oil in the torque converter and high temps will destroy the trans eventually.
                            As the oil gets hot,viscosity lowers and as the trans changes up a sudden short rev rise (flair) happens which is detrimental to the clutch packs as the friction surfaces slip rather than gripping as they should shortening their life.
                            This was explained to.me by an auto mechanic.
                            The whole thing is bizarre. I wrote to Toyota asking the question to no avail. Never been an issue apparently. When I'm towing my van, mostly in fifth as it a very small one, I watch the rev counter like a hawk and soon as the revs rise as it drops out of lock up I shift back to fourth and and up into fifth again when it will hold lockup.once more.
                            I don't have a trans temp gauge but I think keeping in lockup should avoid premature failure.

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                            • #29
                              I have a 2013 V6 so has the factory cooler, and I find it interesting that the box runs hotter just putting around town than it does towing my 2.4 tonne trailer on the highway.

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                              • #30
                                Originally posted by ExNissan View Post
                                Hi mate,
                                I notice this overtemp change down predominantly on hwy or sometimes very fast dirt. Under most driving conditions Dave's 'tuna is usually running a bit cooler than my Prado hence my interest in airflow differences. The difference between the two cars seems to be become significantly more pronounced the higher the speed.

                                As for what gear, I've got a GX so your setup may be different, if you put it into S6 and and drive it up to say 100km then change to S5 if the rpm changes it was in 6 otherwise 5th or below. Its a dodgy way to do it but it makes use of the fact that S mode is really just offering driver suggestions to the transmission control unit which it may chose to ignore. S6 is basically drive with possibly slightly more agressing shifting IMHO.

                                Once you do this a few times in the 80-110 speed range you will get a feel for 4,5,6 gear RPM's at a given speed. Flick it back to Auto and you should be able to make a pretty reliable questimate as to whats gear its in.
                                Lock up is easy to detect - if the TC is unlocked a slight throttle change will cause a change in rpm that isnt in sync with a change in road speed.

                                As an aside I've had a brief look into determing actual gear and lockup status via OBD but it didnt look to be immediatly obvious, If time permits I'll have a bit more of a look but my plate is pretty full right at the moment.
                                TY mate,

                                I can sense when the clutch is unlocked on hilly roads. Trying to accelerate uphill, revs go up but the system feels like a sponge, and temps rise over 100C.
                                If I have time next weekend I'll go for a spin in the farmlands and try S4 & 5 to see if the lockup performs better.

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