I just got a Scangauge II and I was wondering what is the normal range of trans fluid temps?

What is the upper temp limit?

Truck is 97 SC XLT 4X4 4.6L 3.55LS with factory tow package.
Gibson Cat back exhaust is the only mod.

 

Anywhere from 150 to 220 would be typical, depending on the specific driving conditions.

The default PCM programming doesn't post a fault code until it hits 270F for your era truck.

 

Thanks.

I'm doing pretty good right now then.
Driving around today I was running at 120-125 on the highway, up to 135 in stop & go traffic.
It's pretty cool here yet, in the 70's today.

If the PCM won't set a code until 270, what should I be looking for while towing?
What temp would you begin cooking fluid at?

I'd think that by the time you get to 270, the fluid would already be cooked.....

 

Fluid is tougher than the marketers of coolers and such add-ons would have you believe.

 

These guys are niether makers of coolers, nor lube marketing folks ...

http://tccoa.com/articles/tranny/trannyg.html

http://tccoa.com/articles/tranny/merconv.html

http://tccoa.com/articles/tranny/trfluid.html

"And since fluid life is cut in half for every 25 degrees increase in temp about about 170, it's best to know the hottest fluid"

--------------

http://www.amsoil.com/storefront/atf.aspx

Note the temp ranges in which these tests are conducted: e.g 4-ball wear @ 75deg C = 167 def F. This is NOT a coincidence.

@ 270 deg F yer fluid is basically well on it's way to being damaged. But - I doubt you will ever see that.

Keep it below 200-220 deg F and change it at regular intervals. Do not believe this lifetime fluid crap - most folks are actually in the 'severe conditions' category for maintenance intervals.


MGD v5.0

 

You might want to notice that the references at that site are about 12 years old....and the car that is the subject of that site has been out of production that long.

I'm not saying that it's okay to run very hot as I do agree with your suggested operating range. I'm simply pointing out what Ford set as the threshold for posting a fault code.

 

Hello.

Understood sir - and I'm not disrespecting you.

The trannies in question are still very similar in fundamental design, and hence still possess the same frailities. In ddition I beleve the OEM MerconV formulation has likely improved ovet the years, but being a semi-synth it will still have over-temp limits - only a switch to something like the Amsoil product or similar will extend the 'buffer' of hi-temp operational safety - for the oil - but not for the tranny itself.

As for the Ford-specified temp setpoint - I had no idea it was that high - thanks for that.

Just for fyi, Here is an excerpt from TP's site - for the OP's reference :

"Even with the auxiliary transmission coolers that come with factory towing packages & with heavy-duty cooling packages from the factory on trucks, SUV's & performance vehicles, your transmission fluid will *still* overheat in those conditions, because they are all *passive* coolers, with no airflow of their own, no type of active & positive thermostatic control to prevent overheating of the transmission fluid, and no way to accelerate the cooling of overheated fluid.

This is an especially critical issue with Ford automatic transmissions, which use shift solenoids attached to the valve body, as these shift solenoids are constantly bathed in the hot transmission fluid. Fluid temperatures over 190-200 degrees causes premature failure of the shift solenoids (which were a bit "weak" anyway up until about the 2000 model year or so), as well as premature wear on the friction materials such as clutches, steels, bands, etc.

Transmission fluid temperatures rise very quickly in a number of different driving conditions, for example, take an F-150 (or just about any other half-ton truck or SUV) towing a 4000 lb. load........... starting off from a stoplight and accelerating up to just 55 mph will add 35-60 degrees of heat to the automatic transmission fluid in less than 2 minutes! Another example is if you are drag racing, pulling up to the line at a nice, cool 180 degrees of transmission fluid temperature, at the end of just 1 pass down the 1/4 mile those fluid temperatures easily top 240-260 degrees! And once the transmission fluid is overheated, it takes a *long* time to cool back down, and the fluid is of course already damaged at that point. It only takes one occasion of overheating the transmission fluid to initiate molecule shear & start breaking down it's lubricity. Molecule shear happens quickly with non-synthetic transmission fluids, and causes lubricity breakdown & accelerated clutch wear, etc."

Cheers everyone

MGD v5.0

 

Thanks for the info.
I'm the F150 towing 4000lbs example for sure.

I just had the Trans fluid changed and I've been changing it at 30K intervals.

The heaviest trailer I tow is about 4K, and I usually tow that about 6 or 8 weekends a year.

 

The highest i have gotten mine is 180 and with the stress my tranny has to put up with all the time because of the tires, i am assuming that is pretty good. thats only after i have been driving for several hours though and i rarely do that. day to day temperatures are about 120-130 max. I was always curious what the normal range was for these trucks.

 

To add to the discussion, I already have a lot of experience with this issue having been towing gross combined weights of over 12,000 lbs with an 02 Screw and having a custom built 4r70 with heavy duty build.
First, where is the temperature being measured? It's important as a reference to max temperatures.
Next, what measures have been taken for aux cooling?
The max temp seen by the fluid is right out of the converter and can be quite a bit higher than what in measured in the pan or the valve body.
What you see for temperature reaction in the pan to load is quite different than if monitored right out of the converter.
For example pulling on the level then down shifting on a hill with converter temp monitoring will see a much faster and higher temp reaction to increases in loading as well as faster cool-down when the load is reduced. Temps often can go into the 260° range for the duration of the heavy pull.
I have yet to see any obvious signs of fluid deteration over the long term from these swings vs load.
To add more about my peticular setup, I run a deep pan for extra system fluid capacity as well as a fan cooled aux cooler set to run at 185 and will run at slow road speeds.
This fan does another function of cooling the engine bay after shutdown on very hot days by having it's thermostat set to 185 in an engine bay that often gets much hotter after the motor is shut off and no cooling fan air is being pulled through the area.
Bottom line is the good trans fluid is more hardy than one might expect as long as it's not carried to far to often.
Some other items to consider is the cooler lines can only flow just so much fluid volume at pump pressure making aux cooling have a limit as to how much cooling can even be done.
Next, remember the fluid from the converter goes to the radiator first where it can only cool to 'about' the coolant temp and that is usually still 190 to 210 so an aux cooler is the only way to get it down before going back to the transmission.
The pan area does not cool very much but you see an average temperature that often does not very much or very slowly as long as the load is being pulled.
So you see the differences in where the temp is measured, what the temp swings can be and why.
I would very much agree that 270° as sensed by the valve body for very long and often has already degraded the fluid and already begun to burn the bands and clutches at shift times where the lock and unlock of the friction material has the greatest heat generated.
A "stock" trans will only take just so much abuse before something gives up and it's not always from heat. For example, pulling a very heavy load up a steep hill in low gear and wide open throttle is very apt to sooner or later 'baloon' the converter from engine torque even from the little 4.6L. So you can only push it just so far before expecting an issue to develope.
Admittly these are extremes but it a good chance to get a reference idea of how much you can do and get away with it for a reasonable amount tof time.
These are the things that are learned by experience.

 

So according to Mike Troyer, 180 degrees is considered a cool temperature. That being the case, most of us have nothing to worry about.

This is true. As I monitor my ScanGauge II, I notice that the transmission fluid temperature takes longer to come up in temp, but also takes longer to come down.

 

As measured at the hottest point - the tranny outlet line to the cooler, as close to the tranny as possible.

NOT as measured by the SGII (via the PCM sensor in the pan area). The former is significantly warmer than the latter. 180 F indicated on a SG II is likely well north of 200 F in reality in terms of actual fluid temps.

MGD v5.0

 

In my area I beat it fairly good in the mountains such that the trans is out of OD on long hills.
The fluid temp, as monitored just out of the converter, will run as high as 210 depending on the ambient temp. As soon as it upshifts to OD the the temp comes back down in the 150-160 range within minutes.
The fluid will take high temps as long as it's not a normal long term condition.
A big part of the issue is the bands and clutch linings don't like the high temps and can begin to glaze, causing increased slip that heats the fluid even more at these friction points.
As lining material comes off and suspends in the fluid, this in it'self causes more slipping and things begin to get out of hand.
Lining areas are supposed to be porus for friction purposes. If the burnt material suspended in the fluid fills back in the pores of the lining, this is part of the glazing that happens.
The point the linings begins to lock up and unlock are the times the greatest heat is generated at their surfaces. This is all independent of the heat generated by fluid shear in the converter.
If the fluid is already hot, the lining don't have much of a chance with hot fluid being pumped out of the pan area.
The rest is history.