Transmission temperature sensor

[SoNic67]

AX4N transmission. Reading the internal transmission sensor via OBD - does anybody have ideea how reliable is the reading?

I have read on my "noisy" transmission some 385 deg F!!!
That might be the case (I think I have a differential rumbling) but on my Explorer I am reading 312 deg F and it has an auxiliary cooler - that is still too much from what I read online.

LE: Nevermind, it was from the software that I was using - I updated Torque to 1.4.90 because:

Changes:
ELM323 support
Screenshots to Google+ fix
Transmission temperature fix
AIDL plugin API update
Wider fault code support
Accelerometer/GPS fixes
Internal PID calculation support

It shows 160 F now (a short drive, engine at the 198 F temperature)... I will check again tommorow after a longer drive.

[Bigdogg2830]

thats much better. temp should be below 200 f at all times.

[SoNic67]

I did drive the Explorer today to get a baseline and transmission temperature was in the 140-150 F range (155 shortly when I "punch it").
Tommorow is the Sable turn to monitoring.

[T_swensen]

Originally Posted by Bigdogg2830

thats much better. temp should be below 200 f at all times.

I wouldn't say that necessarily. Since you have the cooler that is integrated into the radiator, I would say that the temp shouldn't go above 210-220F just based on engine coolant operating temperatures.

High temperatures are mostly bad because they break down the transmission fluid and allow for wear to occur. Higher operating temperatures means that you need to increase how often you are getting your transmission serviced. (Or you might need to add an auxiliary cooler.)

[Bigdogg2830]

Originally Posted by T_swensen

I wouldn't say that necessarily. Since you have the cooler that is integrated into the radiator, I would say that the temp shouldn't go above 210-220F just based on engine coolant operating temperatures.

High temperatures are mostly bad because they break down the transmission fluid and allow for wear to occur. Higher operating temperatures means that you need to increase how often you are getting your transmission serviced. (Or you might need to add an auxiliary cooler.)

the engine temp is a whole different beast. a good trans temp should be around 140 - 160 f

[SoNic67]

Today the Explorer shows 157 F at noon (90 F outside). But it has a suplemmental cooler.
For the Sable, without that cooler, I was expecting something close of the water temperature (190-200 F)- I will test that tomorrow.

LE: It got up to 178 F on rush hour traffic - water temp was 189 F.

[SoNic67]

Mercury Sable data (air 80F, raining):
Highway, 65mph - water 180F, transmission 156F.
Stoplights, traffic - water 188F, transmission 176F.

Looks like the airflow (on highway speeds) cools the transmission (bottom of transmission oil pan). Not so much at stoplights

[dlc360]

I have a SHO ATX cooler mounted under my radiator on the header panel and disconnected the stock cooler tube. My fluid runs from the trans, through the radiator cooler and then to the aux SHO cooler and back into the trans. I also have a digital temp gauge to monitor the trans temps. When you dont have a fan behind a trans cooler it doesnt do alot in traffic, you need air flow over it to cool the fluid. I have noticed temps as high at 195 / 200 AFTER highway driving while sitting in traffic, but as soon as the air flow picks up it will drop the temp. In the past couple weeks going to shows I have noticed some interesting temps.

After 1 hour on the freeway at 70mph with an air temp of 65-70 the trans was at 150/155. after getting off the freeway I was on back roads doing 50mph and ran through some fog banks, dropping the temp fast to 130/135. Later in the day the air temp has in the high 90's. At 70mph on the freeway, the trans was running at 180/184. I have also noticed that up and down hill stretches will change the temp as much as +/- 2 deg. and following traffic on the highway will also change the temp as much as +5 to 10 deg depending on how close and how long i'm following them. Another thing that changes the temp is if I am running cruise control or not. With cruise on, it seems to run a few degrees cooler.

I have been told the best temp for our transmissions on the highway is between 160 & 180. Its true that heat will breakdown the fluid and in turn cause trouble in the long run. My '99 trans ran so hot that it would steam anywater that got onto the original tube cooler before it finally burned up and destroyed itself.

[chartmaker]

Originally Posted by SoNic67

Mercury Sable data (air 80F, raining):
Highway, 65mph - water 180F, transmission 156F.
Stoplights, traffic - water 188F, transmission 176F.

Looks like the airflow (on highway speeds) cools the transmission (bottom of transmission oil pan). Not so much at stoplights

The design of the heating/cooling exchanger in the rad is intended to make the tran fluid about the same as engine coolant. Steady state temp of trans helps it run consistent.

In the early days of automatics there were some air cooled trans. The radaitor temp stabilization has been around for a long time for a reason.

-chart-

[SoNic67]

From what I saw on the Explorer and Sable, an additional cooler without a dedicated fan does nothing in normal traffic (excepting here pulling a trailer).
On highway there is not enough heat generated to matter - the bottom of transmission pan looks like is enough surface to allow cooling of fluid under the water temperature.
On stop-and-go traffic, there is not enough airflow in the auxiliary cooler. An electric fan with thermostat would help there. Without, looks like the bottom of the transmission still helps cooling if the car moves with some 35mph...