Trans temp w/ Scangauge

[kwaapia]

Transmission temperature by scangauge - my $0.02

Having the transmission temperature sensor available is one thing, getting the data from the ECU is another. No doubt about it, the sensor is available in the vehicle. The sensor provides a voltage to the ECU, and the ECU calculates the sensor resistance from this voltage by using the well-known Ohm's law. From the sensor resistance, the ECU uses a look-up table supplied by the sensor manufacturer, to match the resistance to a temperature.

The problem with the LC is that the ECU should be called a powertrain control module, in that it performs the task of running the engine as well as the transmission and probably also the transfer case. The proof of this lies in the fact that there is no separate control module for either the transmission or the transfer case.

So if the ECU does all these calculations internally, it doesn't have the need for sending the data to the outside world. Of course, if you knew what command to send, you could retrieve the data from the ECU.

Toyota did not make this ECU, it is from Nippon Denso. They are the ones who would know, and I am 100% sure Nippon Denso engineers in Japan, if you could find one who spoke english, will not give out such information.

What Scangauge can do:

Get a new trans temp sensor, and figure out the voltage/temperature curve. Then provide 1 analog input channel for the scangauge, as well as a socket which will split the voltage wire from the sensor into 2 parallel lines. One still goes to the ECM, the other connects to the analog input channel of the scangauge. With the curve stored in the software, the gauge can then measure the voltage, convert it to a temperature and display this data.

Personally, I don't think scangauge will modify its product just because some folks want to get information they shouldn't really be worried about.

The information you would get will not be useful to anyone. If you overheat the tranny, the warning light comes on. That should be enough for a smart driver to pull over.

 

[Brian894X4]

By that logic, why have an engine temp gauge. Why not just an idiot light.

Well....I guess our stock gauge really isn't much better than idiot light, since it's designed to read the same temp for a wide range for...idiots.

With the Scangauge people have noticed that a good temp range for the 80 to run in mild temps is around 185. If you're seeing 200-210, your stock gauge may not move, but you know something is wrong and you can look into it before it gets worse. Could be a failing water pump, radiator or thermostat, etc.

Same thing for the tranny. Tranny could be losing fluid and heating up or being overstressed. Once you learn what normal is, when you see higher than normal temps you can figure out something is wrong, before the light comes on, by which time, either damage has already been done or you're out in the middle of nowhere.

I'd much rather see my temps were fluctuating too high while close to home than have the light come on in the middle of the desert hundreds of miles from anywhere.

Since the Scangauge probably won't ever work for this, I'll be looking into a regular trans gauge somehow.

 

[TOY350]

er ive got a scanguage 2 but i think my FZJ 80 is OBD1 were is the obd plug so i can try and hook it up?

On 95-97 rigs it is located by the fuses under the fuse cover by your left knee while in the drivers seat. Not sure if 93-94 had the OBDII option.

 

[kwaapia]

The reason why a temperature gauge is in vehicles is not because the manufacturer wanted to do so, but because of regulations by know-nothing bureaucrats trying to tell engineers what they think should be available to a driver. Another example is the check engine light, which many drivers ignore completely.

Transmission temperature will fluctuate with vehicle load, with the driving terrain and with the outside temperature. It won't tell you anything about your transmission you need to know while driving. Focussing on the road ahead, is more important and safer than monitoring some gauge while driving.

Would you like to know the exhaust back pressure, the in-cylinder pressure, the water pump rpm, or the temperature of the tires as well? How about the carbon dioxide concentration in the passenger compartment? All this information is available. If you want to monitor that as well, you should be flying, not driving.

Some of you have too much time on your hands.

 

[Pak Meul]

I put a temp guage on a vehicle once. I used my spare time to figure out that heating up the conventional fluid once allowed the trans to slip between gears and had essentially ruined the fluid. After getting hot once, it got hot much more quickly than it had before it got hot the first time. I then spent more of the free time I had on my hands to put a larger cooler and switch to synthetic ATF.

The trans temp guage was then useful for showing me that I had made a wise decision to take care of my trans before I ended up with major problems and huge repair bills. A little time looking at a guage saved me the major time of replacing a trans or having my family stranded in the desert because I didn't know that the fluid was hot enough to cause damage.

I'll never tow without one. I wouldn't badmouth others for wanting to know what their vehicles are doing either.

BTW I never crashed while glancing at the guage. Maybe some of us can walk AND chew gum.

 

[Brian894X4]

The reason why a temperature gauge is in vehicles is not because the manufacturer wanted to do so, but because of regulations by know-nothing bureaucrats trying to tell engineers what they think should be available to a driver. Another example is the check engine light, which many drivers ignore completely.

Transmission temperature will fluctuate with vehicle load, with the driving terrain and with the outside temperature. It won't tell you anything about your transmission you need to know while driving. Focussing on the road ahead, is more important and safer than monitoring some gauge while driving.

Would you like to know the exhaust back pressure, the in-cylinder pressure, the water pump rpm, or the temperature of the tires as well? How about the carbon dioxide concentration in the passenger compartment? All this information is available. If you want to monitor that as well, you should be flying, not driving.

Some of you have too much time on your hands.

Everything fluctuates, such as oil pressure, voltage, engine coolent temp and trans temp. That doesn't mean the gauges are worthless. Once you figure out what the normal parameters are for a given situation, speed, ambient temp, you'll see when something is wrong.

The idea is to give people advanced warning of potential issues. If that's not your cup of tea, you're definately not the norm around here.

 

[Cruiserdrew]

I agree. Modding the temp gauge was one of the best investments of an hour ever. I learned that my truck ran hot uphill with a load. I just finished swapping the radiator today. I got 11 years out of the first one, that's not too bad.

I do understand why Toyota and I suspect other mfgrs engineer a dead spot for normal, because once you know it moves, you watch it all the time.

I would like to know trans temps, just to keep an eye on things.

 

[e9999]

just spent several days wheeling and towing in the desert.
Was keeping track of my ATF temp. Fluctuates widely. From 140 on a flat freeway towing to about 200+ wheeling in sand in Hi. Notably, I did see a big drop in ATF temp from 200 to 170 or so just by switching from Hi to Lo in sand while maintaining the same speed. I did not want to go above 200 so I did something about it. The coolant temp dropped some too but not as much. There is a chart floating around here that shows life expectancy vs temp for ATF. Big difference.

 

[97lx450guy]

Anyone know the operating temperature for for the transmission. Just standard city driving? Just installed a gauge

 

[flintknapper]

Anyone know the operating temperature for for the transmission. Just standard city driving? Just installed a gauge

Depends on your driving habits and ambient temp. My transmission (in hot summer temps, city driving) will be between 145-155° F.). Highway....about 140-145° F. (if not towing or not climbing hills).

Yesterday, (ambient about 55° F.) I drove 20 miles to town (highway) and the tranny temp never got over 105° F. In town about 115° F.

Even towing a trailer (about 3K lbs. total) I've never seen temps over 162° F. from my A343F.

I have a sending unit in the transmission pan and a digital Auber gauge in the dash.

Digital Trans Temp Gauge Install........


IF your transmission is in good working order...then all in all...its a pretty boring gauge. The 343 runs pretty cool. Temps will rise slowly anytime your Torque Converter isn't locked up, but it goes back down pretty quickly once it does and once you get some air moving through the transmission cooler and tranny tunnel.

Aside from towing, sitting in traffic is when I see my temps go the highest, but it never gets very high.

 

[half k cruiser]

@LandCruiserPhil not sure if your still running a scangauge or not. My gauge is currently hooked into my wife's 04 GX and I don't feel like pulling it out. If your able to program gauges on yours I have the following code that works for ISO. You might give it a shot and see if that will pull the transmission temp data for you.

TXD: 686AF101B4

RXF: 044105B40000

RXD: 2808

MTH: 00090005FFD8

 

[alia176]

@LandCruiserPhil not sure if your still running a scangauge or not. My gauge is currently hooked into my wife's 04 GX and I don't feel like pulling it out. If your able to program gauges on yours I have the following code that works for ISO. You might give it a shot and see if that will pull the transmission temp data for you.

TXD: 686AF101B4

RXF: 044105B40000

RXD: 2808

MTH: 00090005FFD8

Wow, is this the voodoo code for pulling tranny temp out of our 80 tranny temp sending unit?

 

[Joshwho44]

Wow, is this the voodoo code for pulling tranny temp out of our 80 tranny temp sending unit?

This doesn't work for the 80. The diagnostic PID for trans fluid temp isn't in the ECU, so there is no way to get the info over the OBD2 port.

I installed an analog temp gauge from Hewitt Industries last year and it has been working great. The temp sender even has the same thread as the OEM sender! You can simply unscrew the factory sender and zip tie it out of the way, while keeping it plugged in to the harness. FYI, it was incorrectly stated earlier in this thread that the trans temp sender affects the TC lockup/ OD, but this is not the case.

 

[Tools R Us]

Anyone know the operating temperature for for the transmission. Just standard city driving? Just installed a gauge

Likely don't want exceed ~250F ish. IIRC, the light comes on at ~300F, so that is where Toyota suggests getting out of the throttle.

 

[Tools R Us]

...
IF your transmission is in good working order...then all in all...its a pretty boring gauge. The 343 runs pretty cool. Temps will rise slowly anytime your Torque Converter isn't locked up, but it goes back down pretty quickly once it does and once you get some air moving through the transmission cooler and tranny tunnel.

Aside from towing, sitting in traffic is when I see my temps go the highest, but it never gets very high.

Agree, the cooler is very well setup, nice system. Did a bit of playing, stressed it pretty good, never saw temp even close to anything that I would worry about, so passed on the gauge.

 

[Travis351]

I was long haul towing about a 4,000lb boat last month and checked the temperatures running 65mph with overdrive on, and then off and noticed that the transmission stayed much cooler with the OD off. More specifically, about 150 with it off and hovering around 200 with it on.

 

[half k cruiser]

This doesn't work for the 80. The diagnostic PID for trans fluid temp isn't in the ECU, so there is no way to get the info over the OBD2 port.

I take it you have tried it then ? Or can you explain what is monitoring the trans temps from the factory ?

 

[half k cruiser]

Wow, is this the voodoo code for pulling tranny temp out of our 80 tranny temp sending unit?

Apparently not according to an above post, but i'm hoping someone will or has at least tried it to confirm.

 

[inkpot]

I was long haul towing about a 4,000lb boat last month and checked the temperatures running 65mph with overdrive on, and then off and noticed that the transmission stayed much cooler with the OD off. More specifically, about 150 with it off and hovering around 200 with it on.

Higher rpm w/o overdrive, so I would expect it to be somewhat cooler. Either number is pretty good.

 

[Joshwho44]

I take it you have tried it then ? Or can you explain what is monitoring the trans temps from the factory ?

The ECU is doing something with the sensor input, as it triggers the dummy light. I'm not sure if there are any shift schedule adaptations for ATF temp, but it doesn't seem like it... I don't notice any difference with the factory sender unhooked. Even in 1997, OBD2 was relatively new and the automakers weren't invested in custom PIDs. You have to keep in mind that data available on the OBD2 port was a regulatory requirement, intended for emissions purposes.