Normal transmission temp

I just got a scanguage II, and I appear to be reading trans temp in my 99 with a a x-code I found. Just wondering what normal transmission temp is on the A340E transmission. I can't seem to find it anywhere. My the highest my guage has read is about 180-185

 

About the same as the engine. Excellent. See what it reads with a load on a hot day on a grade. Could approach 300.

 

On an extended trip, this read about 212 at the highest. Is that normal? I read the a/t temp warning light flips at 250. It's making me want to put a trans cooler on it haha

 

Anybody know?

 

Normal fluid temperature in transmission to be 175 deg. F.

Rate of oxidation to double for each temperature increase of 20 deg F above normal (175 deg F). As oxidation rate doubles, useful life of fluid is cut in half.

At 175 deg F life is 100,000 miles
At 195 deg F (20 deg above 175) life is 50k miles
At 215 life is 25k miles
At 235 life is 12k
At 255 life is 6,250
At 275 life is 3,000
At 295 life is 1500
At 315 life is 750

At temperatures much above 300 deg F the metals in the transmission will tend to warp, twist etc. high temperatures causes the formation of varnish deposits which impair or pre vent transmission operation.

At a fluid temperature of 415 deg F fluid life is 30 minutes!

Source: Empire Lubricants Inc.

 

I have a Scan Guage with your transmission. Trans temp seems to approximate coolant temp - in my case about 183 degrees in Phoenix - because of ATF cooler in the radiator. In 255K miles, no issues. I still however plan to install an auxiliary cooler.

 

What code did you put in? Cause the 3 I found on a few different forums all works and it is reading. I was cruising for quite a while at about 185 and then right before I got home the reading started creeping up and when I got home it was 212

 

I'm gonna get a pryrometer and check this reading against the trans pan temp. It should be close. Like I said I found the same code on like 3 different forums and it is pulling a number

 

So testing this code, it was the same temp as water temp this morning, which tells me it is pulling a temp. And the temp increases until I get to cruising speed, then it will start to come down. And it rises a little every time the torque converter unlocks. So it seems to me that this is definitely trans temp

 

I watched my scanguage go all the way up to 215 on trans temp, but no higher. This is at night, city driving for a while. Thats kind of high is it not?

 

I am thinking thats a little warm . is your truck bed empty ? Are you positive thats a transmission temp reading and not engine coolant reading ?
Do you know what temp your coolant thermostat opens up

Less heat when the converter is locked but stop and go driving will drive the temp way up . The torque converter is the hottest part in the transmission . When trans fluid leaves the torque converter , fluid is sent through the upper cooling line to the rad to be cooled then sent back to the pan . The trans temp sensor is mounted to the valve body inside the pan . The temp you see on the scan guage is after the fluid has been cooled .....Dont quote me on this until I get into my manual and double check where the sensor is lol

 

That's means it's even hotter in the pan! Lol. I'm pretty sure this is ATF temp. I got the same x-code on 4 different forums. It does drop a lot when hit O/D and it locks, then heats back up when it unlocks. The scangauge reads my water temp, and it's not the same reading. Cold this morning it was, which leads me to believe it is indeed a temp reading, but the water temp heated up a lot quicker. When the trans temp was at 215, water temp was about 195. Idk exactly the thermostat temp, but from what I've seen it opens around 180. The temp has been staying from 185-195. And yes my bed was empty

 

http://www.amazon.com/Long-Tru-Cool-Transmission-Cooler-4454/dp/B005XZXB1M


In my books , you are running on ther warm side . With nothing in the box of the truck , I would be wondering if your trucks trans cooler within the rad is performing at its best .
There are two locations to install a transmission temp sensor . One is in the pan and the other is on the hot torque converter line going to the rad . You are seeing the colder transmission temp with the sensor mounted to the valve body .
Can you imagine what the temp of the fluid is coming out of the torque converter
Cheapest bet is a good quality trans cooler like I posted above . There was a guy on here selling them for 30 bucks if he has any left. Living in Florida , the bigger the better. The aftermarket cooler I linked to is fairly small

 

I saw his thread, and I'm planning on getting one now. I will probably bypass the internal cooler in the radiator and just go straight to the cooler. I have towed with this truck for quite a distance and the trans overheat light never came on, which tells me that it never reached 250 degrees which is when it's supposed to trip. I could feel the floor getting quite warm though so I know it was getting warm. That's specifically why I got the scanguage. To watch trans temp. It seems to stay around 180 for a long time, but with a lot of stop and go it climbs to the 200s and stays up there. Never seems to go over 215 though

 

Apologies for reviving an old thread. I've noticed that my scanguage AT temp tends to dramatically increase when i let the gas off the pedal at highway speeds - such that when I get to the bottom of a freeway offramp my scanguage temperature may go from 150 degrees (where it hovers on the freeway) to 175. Is it normal for the fluid to go up when you coast? It's not always so dramatic but it will always steadily go up when I coast even if i'm already at a higher temperature.

Other notes:
I don't coast in N; this is all while in D (overdrive on)
Around town driving my scanguage will often hit numbers above 200 after warmed up (highest i hit was 240 going up a 4 mile steep hill on a cool day)
My transmission tends to do a very slight but annoying jerky shift when done around 2000-2500 RPMs (I've been driving with the 'power' button and this makes things smoother, perhaps because it just shifts above the problem zone)
Transmission was rebuilt 40k miles ago under previous owner
Normal engine operating temperature is 200-204 degrees (as read by scanguage)
2002 Tacoma TRD 130k miles

 

These trucks run too hot without an aftermarket cooler. I was running over 200, sometimes 220 just running around town. When I had the cooler installed it rarely went over 200 and it cooled down quick if it did. But to answer your question, yes, it is normal for your trans temp to go up while coasting. On the highway, your torque converter is locked up which cools the trans. When it unlocks it heats up the fluid

 

@smmarine I am wondering what the specs on your truck are. I have been trying to read the trans temp on my 99 2.7 with the a340e transmission but I can never get a response from the OBDII. I believe you have the a340f since you have 4wd but I don't think they are wired any differently since the wiring diagrams are identical.

 

With a transcooler cooler, my temps stay sub 170 until I get into city driving/traffic. The highest I've seen so far was on an 90F day in traffic, got into the 190's. Without a fan on the cooler, theres not much you can do on a hot day in stop and go traffic.

 

What are you using to get it? I was able to pull the trans temp with a Scanguage on my Prerunner with the A340E. My current truck does have the A340F and it will not read the trans temp. Some years had a temp switch that just turns on the idiot light on the dashboard, and some actually have a sensor.

 

I'm using a carista bluetooth adapter connected to an iPhone running OBD Fusion. It can take custom PIDs. I actually also purchased their extended PIDs for my year, which included the trans temp. But when scanning for matching PIDs, the trans temp is not one of them. I can read a lot of other useful things like IAC duty % and even what gear I am in.

I got the PID info from this thread which was actually acquired from the xguage codes

Mode: 01
PID: B4
Formula: A*(9/5)-40
Min Value: 0
Max Value: 300
Description: (I used TFT, but you can put in whatever you like)
Unit: F (if you want, you can put in the degree sign so it's °F).

The temperature sensor is the same part number from 96-04. From what I have read it is more about how the ECM reads the information. I have the 99 FSM and it shows how to test the sensor with difference resistance readings at different temperatures.

Is your 99 Prerunner a california spec model? I'm just trying to decipher what makes the temp readable.