I know there are quite a few of these, but everywhere I look I see different information.


As you can see in my signature I have a '99 V10 Automatic. After buying our last TT I thought I should figure out a way to monitor my transmission temperatures so I got a SGII. My plan was to see how its performing and then decide if I need to install a cooler since the 99s didn't come with great cooling. Finally worked the truck fairly hard over the weekend towing our TT (~7,000 lbs) up 395 to Crowley Lake which includes a 6% grade up to the Sherwin Pass.


Temperatures outside were above 90 the entire drive and my transmission was around 175-190 with various small hills and flat areas for the first part of the drive. On the Sherwin Summit the coolant and transmission both climbed to around 210 and didn't go any higher. I was able to maintain 45 and only heard the fan kick on twice. Both temperatures stayed between 200 and 210 on the 8 mile climb. I thought staying under 210 for the transmission was fine, but after some research I'm seeing that there is concern going over 200 on the transmission temperatures.


It was between 90 and 100 AOT on the way home and I never saw the temperatures on the transmission get over 200 even on a few smaller hills. So considering the outside temperatures am getting my transmission too warm, or do I have nothing to worry about?

 

There is NO concern at 210F transmission temperature from people that actually know something about the transmission. There is a lot of concern from people that think there is something magical about 200F that should never be crossed. Ignore them, they have no facts to back their stance.

Where you might run into transmission temp problems is backing a trailer. There is very little airflow over the cooler, and without a cooler in the radiator you essentially have no transmission cooling when in reverse.

 

Thanks Mark! Good to know from a trusted source I have nothing to worry about.


I've heard about issues with backing a trailer. For that reason I usually put the truck in 4-Low and since I don't have ESOF it just puts it in 2WD low. Plus myself, or my wife (since she usually backs while I direct), can maneuver at a more reasonable speed without feathering the throttle as much.

 

So what temp don't you want your tranny to go over??

 

The max you want to see is 250F.

 

What happens above 250?

 

There are plastic parts in the torque converter and transmission. They get softer above those temperatures. It's not good for them, but I wouldn't expect them to fail as soon as you get above 250F. I'd never want it to get out that I've tested transmissions as high as 320F, and I've posted on here a few times about an off road race 4r100 that got hot enough to melt the solder out of the solenoids. And it still worked, and we won the race.

By the way, solder melts at 450F.

 

Thanks. I've never seen anywhere a reason why one should stay beneath the 250 mark, only that it should not be exceeded.

As I remember, up to 220 should be considered normal with no need for concern. Above 230 is ok for 30 min at a time (please correct if thats not correct).

Is there any need for additional maintenance for a transmission that exceeds 230? Once? A few times? Frequently?

Clearly, if it is frequent one should look at additional cooling, but can more frequent fluid changes prolong transmission life when living at the edge?

 

I have used this as a guideline. Below 220 deg F is no worries. 230 deg F is the upper limit I ever want to see and for not too long. Above 240 deg F is when internals and fluids start to break down. It is always a temperature over time formula.

Transmission Life Expectancy - TCI® Auto

 

No worries?! That chart says my transmission would only last 20,000 miles at 220! That would worry me, especially considering how my transmission has a thermostat that regulates it to 200 degrees nearly all the time. Does that mean it's only going to last 50,000 miles?

I've seen that chart before, and I don't think it has anything to do with reality.

 

I tend to ignore the horizontal axis numbers. I look at what happens on the vertical axis with temperature.

 

Interesting. I recently towed the boat about 400 miles. On the way out the outside temperature was mid to upper 90's. My trans temp stayed right about 201. Climbing a few steep hills, in 4th the temp went up as high as 206. On the way home it was night and the outside temps were below 75. My trans temps were exactly the same. Now I know why.
The F250 seems to run slightly lower temps than the F150s.
According to my scan gauge in my 2008 I would be around 214 in traffic and just below 210 driving with the same boat in tow. I also took that truck mudding and would frequently get the temps up around 230. The truck never seemed to care. Last I know there were 130,000 problem free miles on it.

 

That chart is nothing but lies. Everything I have quoted, above, is lies. Internals and fluids DO NOT start to break down at 240F. Maybe they did 50 years ago, but the modern fluids and materials that are in current transmissions DO NOT have this problem. You're just spreading misinformation.

 

Good to know.

 

Okay, I took note and checked my trucks transmission temps today. Something must be wrong. A sensor might by out of spec? Here are the numbers.

It was 95f today when I got off from work. Truck had been sitting for 9 hours not running. BEFORE I started it I checked the temp. Transmission was showing 124f temp!!! After sitting for 9 hours. Hum.... Not right I would think.

So, after warm up and driving for about 30 minutes. Trans temps were 331 to 335f. And this pretty much where she runs.

I checked the fluid and it was nice and red and clean no burnt smell at all. In fact the fluid has 35K miles on it since the last service. Which was a hot flush and filter change. In other words the fluid looks like new. I have no problems with operation. She runs like a top. I used OBD Link with the green LX blue tooth adapter to my cell phone for this check today. I used to have Torque Pro, but dumped it as it took forever to link to my blue tooth adapter.

Thoughts?

B.