Transmission temp gauge sender..where to install?

[Brian894x4]

According to my '95 FSM, the "normal operating temp" is listed at 158-176F in in some places and 122-176F on another places.

I can't find this info in my '95 FSM, but supposedly for the '94 and older A442s, the tranny idiot light kicks on at 302F and kicks off at 248F.

I wonder of the 343 has a lower kick on point for the light. Can't find the spec anywhere so far, though. One online source seems to indicate that at least the mini-trucks A/T light comes on at 284F

As far as the lower operating temps, it could be the dual factory cooler. The fluid does run through a pipe in the radiator, but all U.S. spec FZJ80 get a huge second radiator style cooler mounted in front of the engine radiator on the driver's side. It's been mentioned that the Toyota trannies do run cooler than the U.S. domestic made transmissions and that may be at least one reason why they last so much longer.

 

[MoGas]

According to my '95 FSM, the "normal operating temp" is listed at 158-176F in in some places and 122-176F on another places.

I can't find this info in my '95 FSM, but supposedly for the '94 and older A442s, the tranny idiot light kicks on at 302F and kicks off at 248F.

I wonder of the 343 has a lower kick on point for the light. Can't find the spec anywhere so far, though. One online source seems to indicate that at least the mini-trucks A/T light comes on at 284F

As far as the lower operating temps, it could be the dual factory cooler. The fluid does run through a pipe in the radiator, but all U.S. spec FZJ80 get a huge second radiator style cooler mounted in front of the engine radiator on the driver's side. It's been mentioned that the Toyota trannies do run cooler than the U.S. domestic made transmissions and that may be at least one reason why they last so much longer.

I got to thinking about this last evening. The temp sensor for 80s is just to illuminate the AT/P light if the temp is too high. That is probably why the Scangauge won't show a tranny temp, It is not a computer monitored or computer controlled. It is just a switch that closes at the high temp and opens at the low.

 

[MoGas]

I can't find this info in my '95 FSM, but supposedly for the '94 and older A442s, the tranny idiot light kicks on at 302F and kicks off at 248F.

I referenced my library, and according to my 91 FSM (A440F): 302F on/248F off, 93 FSM (A442F): 302F on/ 248F off, 94 FSM (A442F): 302F on/ 248 F off.

Dave

 

[Brian894x4]

MoGas, thanks for those specs. So, the 343 is probably set up the same way.

As for the tranny temp sensor, it is actually a variable sender, throughout the temperature range, starting at least at 68F. Since that is a test point. The wiring diagram shows the sender feeding the ECU. I kind of wish it didn't, because that would be a great location to install an aftermarket sending unit for a real gauge.

The Toyota ECU apparently controls the transmissions as well as the engine, instead of a seperate tranny ECU and that's one reason it's more difficult to extract information like this from it.

But the temp sender is a variable sender that sends signals to the ECU so, assuming someone had the proper codes, it should be able to work with the scangauge, but getting those codes has been like trying to steal secrets from the Pentagon.

Maybe we ought to enlist the chinese to hack into Toyota's database for us.

 

[Wagontrain]

I was going to put an A/T sensor in a T where the lines attach to the radiator. The lines there are flex (rubber) and quite easy to get to. This is on a 60 series, not sure if it's the same on an 80.
WT

 

[ntsqd]

Seems to me that an electronics type might be able to design & fab a circuit that makes the OE sender "look" like the the gauge mfg's sender or offset it's Ohm's to match the desired sender's. Then one sender could drive both the computer and the accessory gauge.

Or, can there be a "t" fitting at the stock sender's location?

 

[OMC]

My first post and I hope it is of some assistance:
http://www.automatictransmission.com.au/release.asp?NewsId=12031
I've installed this setup and it works well. Having the temp sensor built into the elbow makes it a simple task to install.

 

[Brian894x4]

Ntsqd,

I wondered that myself. The manual lists the ohm specs for two temps. If the sender is linilear, then I suppose one could calculate the rest of the temp range. Or pull the sender and take measurements.

One thing was brought up about this idea is that it might adversely affect the signal to the ECU. I'd be a little nervous about messing with the ECU in anyway, since they are so expensive to replace.

OMC,

Welcome to the board! That is a neat set up. If my idea doesn't work, I may just as well try to order at least the elbow and put in the sender and gauge I really want to use...which isn't a VDO. But right now, VDO is the only one may work.

We'll see. I'm off to get parts today.

 

[waldrtw]

I would imagine that the ECU is taking a analog signal from the sensor and the ECU would send a digital signal for the OBDII to read so figuring out the code would be pretty hard to do. I guess you could do some sort of scanning the lines with another computer and see what you could find (not real sure if it would work). We are doing stuff like that here at work for Digital control valves.

You should be able to splice into the wires coming from the Trans temp sensor and calibrate it. I guess you could pull the sensor out and take a ohm reading at room temp. Heat it up in the oven to another known temperture and record the values. Then you could feed a B&B analog to dig. box and write some software for your on board computer to show the temp. Should not be to hard to do.

Tim

 

[waldrtw]

Brian,

The sensor should be linear. Not sure if it would mess with the ECU or not.

Tim

 

[ntsqd]

Brian,

The sensor should be linear. Not sure if it would mess with the ECU or not.

Tim

That was my lone fear in trying to read it's output with two "gauges", that the paralleled readers would influence each other. May be acceptable for the gauge, but the ECU could be a rather unhappy camper.

From the link above:
"...there's no use measuring the temperature in the sump after the pre cooled oil has mixed with the oil in the sump as this will tell you what you were doing 3 minutes ago and not instantly like the outgoing cooler union will do."
The issue I have with this is that I don't monitor any gauge so closely that I'd ever catch a temperature spike except by accident. I rather doubt most folks would catch such a spike except accidentally. If it isn't a spike then a pan mounted sender will tell me the same thing. And this still emphasizes the wrong thing, IMHO. Fluid temp isn't what's important as the fluid is easily & comparatively cheaply replaced. Trans internals temp is. That will always be inferred if the gauge is reading fluid temp. Such a monitoring method has a time delay that is variable, so what is the point of an "instant" response?

 

[Brian894x4]

The whole "where to measure the fluid" thing is not really a big deal to me either. If I could choose any place, I'd pick where the factory sender was, because they obviously thought that was the best place. But I think sump temp will still give me a good idea of what is going on.

The way I see it, temps may vary at any given point in the system, but once there's a problem, the temps will increase throughout the system.

I figured I'd run it for a while and see what "normal" is and when things go way above normal, then I know something is up.

The whole point for me is largely curiosity anyway. I'm just curious what the temp readings are going to be and under what circumstances, but knowing that things are starting to spiral upward "before" the temp light comes on, so I can react to it, and lessen any potental damage to the tranny would be a nice perk.

 

[cruiser guy]

The issue I have with this is that I don't monitor any gauge so closely that I'd ever catch a temperature spike except by accident. I rather doubt most folks would catch such a spike except accidentally. If it isn't a spike then a pan mounted sender will tell me the same thing. And this still emphasizes the wrong thing, IMHO. Fluid temp isn't what's important as the fluid is easily & comparatively cheaply replaced. Trans internals temp is. That will always be inferred if the gauge is reading fluid temp. Such a monitoring method has a time delay that is variable, so what is the point of an "instant" response?

This is the same debate we have with the turbo's and pyrometers. I do not check my pyrometer in normal driving conditions but when I'm pulling a hill I know that I'm working the truck and it's going to get hot so I periodically check the pyrometer. It becomes natural to do that. I'm sure the same thing happens with a tranny temp gauge. You'll get a feel for when the tranny will heat up and that's when you'll be keeping an eye on the gauge.

For the pyrometer, I'm not as concerned about how hot the turbo is getting usually, I'm more concerned that I'm not melting my aluminum pistons! When shut down time comes then I'm watching to ensure I don't shut down before the turbo has cooled sufficiently.