Normal temp for an automatic transmission?

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Apr 8, 2006
Birmingham, AL
What's a "typical" operating temperature for an automatic transmission? If anyone, especially other Scan Gauge users, could post their temps and vehicle specs, I'd like to see them.

I have a 5-speed auto (Ford 5R44E) filled with BG full synthetic fluid. I've got a factory trans cooler too. I've had a Scan Gauge since December and have been watching trans temps since then. The operating temp after several miles of driving ranges between about 145*F in colder temps (20*F-35*F) and 170*F in warmer temps (70*F-80*F). I haven't had a chance to monitor the temps in hot weather yet. Most of my driving is around town with a lot of shifting.

At what fluid temperature should I consider a larger cooler or deep pan?
I would try to avoid upwards of 200 deg F for any extended periods. While pulling a long uphill or mountain in 95 deg summer heat and pulling a trailer, you will probably exceed 200 deg temporarily until you go down the other side. I think that sustained temps of 190-195 with synthetic fluid should not be an issue.
If you have a factory trans cooler then you probably have a thermostat on there, meaning you have a 180 degree thermostat on the external cooler that lets the trans fluid bypass the cooler when temps are below 180 degrees, any temps of 180 degrees or higher would let fluid go through the cooler.

If they sell a deep pan and you plan on keeping this vehicle a long time, then it would be worthwhile.

If this trans is speced for Mercon V then at your next fluid change I would recommend Amsoil ATF or Redline D4, both fluids meet the Mercon V spec.

What is the pour point and flash point of this BG Trans Fluid.
I don't know if there is a thermostat on the cooler. I can't see a thermostat just by looking at just looks like a plain cooler you would get at a parts store.

There is a deep pan available. It adds two quarts of capacity and is finned.

I don't know any specs on the BG fluid. I have only heard good things about their products, so I figured their full synthetic would be okay. I have had the BG in for about 12K miles and the truck shifts the same as it always has. The factory fill was Mercon V, which was flushed at 30K with fresh Mercon V. The trans was flushed again at 58K, but with the BG synthetic.
Motorcraft Mercon V is a semi synthetic trans fluid that cost about $7.00 from the dealer. It's a good semi synthetic trans fluid.

I would rate Amsoil ATF or Redline D4 as a little bit better.

I put Amsoil ATF in my Marauder's 4R75W Transmission and noticed better shifting, this trans had Motorcraft Mercon V in there.

Do you remember how much the BG Trans fluid goes for a quart, meaning the cost for a quart of this trans fluid.
Is yours a stacked fin cooler? Some have built in thermostats in them or is a self regulating design like the Long/Trucool ATF coolers.
It's a stacked fin cooler.

I don't know how much the BG was per quart. I had the flush done at a shop. They listed the total price for the BG fluid at $104.92, but didn't say how many quarts were used.
It may have a inline thermostat. But Ford tends to install them. The temps you see are quite normal. I have seen up to 180 if Im really driving it hard around town. When it was cold and I was not pushing it (ice) it would stay around 155. But I have a deep aluminium pan. Going up hills and such it has gone up to right under 200F, which is NBD on synth and a cooler. It drops like a rock on the other side.
The thermostat on my F150 (4R75E) is a square device near the trans itself. Two lines feed in and two feed out.

I have a chart on Ford trannies and regarding the 4R544E, it says:

"Cooler flow is controlled by a cooler bypass valve in the main control (which I interpret as internal in the valve body- J.A.) that will not fully open until 100F. Until 100F, there may be flow out of both ports."

It further specs that full cooler flow is achieved at 150-180 degrees.

If the 5R44E is typical of the other Ford trans' I know about, the temp sensor will be in the valve body and the PCM uses that sensor to delay converter lockup until the fluid reaches a preset temp. I have a Gryphon programmer that reads this temp, but I also have a deep pan with a temp sensor installed. Fluid temp in the pan reads about 15 degrees cooler than the valve body sensor. The really hot oil is coming out of the converter and that oil could be 50-100 degrees, or more, hotter than the pan or valve body (the higher numbers in extreme situations).

In an old GM 700R4 I used to have, I installed sensors in the pan, the cooler out line and the return line. The pan could be 165 and the outlet line could be 240 and the return 140F.

A good trans fluid can handle high temps for short periods but it's the time-at-temp which will really kill it. If it comes out of the converter at 240, a good set of coolers can knock 100 degrees off pretty easily, so it doesn't spend much time at that high temp, but the stuff that stays in the converter may spend more time at the French fry temps (though cool oil is being fed in about as fast as the cooler outlet flow is going out).

Anyway, the long-winded bottom line here, it that the temp you see is not the highest temp in the trans. If you keep in the back of your head that the converter is some 50-80 degrees hotter, you'll have some idea when it's time to back off. I don't worry about 220 or so continuous (in the converter) but if you read 200 in the valve body, then you can figure the converter is 250-plus. In short spurts, even that is not all that harmful, especially with a good oil, but I'd be thinking about backing off of whatever work I was doing to cool the "poor bairn" off a little. If you work the trans this way a lot, consider upgrading your coolers.
I installed a temp gauge on my 2001 Town and Country. First 30-45 minutes of driving the AT would never come much over ambient temps. Here's example from memory:
70f ambient temps
0-20 minutes : 90F
20-30 minutes : 110F
30-45 minutes : 120F
45-60 minutes : floats 160 - 195F

Temp would fluctuate greatly with hill climbs and hard acceleration. If it was cold outside it might never see 160F. However, once it got warmed up, it'd stay up there in the 160-190 range. It'd break 200 easily on a long hill, conservatively driven.

On my 1983 Chevrolet El Camino I can aim my infrared gun at the torque converter.

The torque converter temps are always 50 to 60 degrees higher then the temps in the trans pan.

These are some of the temps recorded during different times of the year:

1) Winter time is ususally between 155 to 165 degrees
2) Spring and Fall is about 175 degrees
3) Summer time is about 180 degrees

These temps were recorded after a 30 mile run, I have a Derale Trans Pan with cooling tubes on the bottom and I use Amsoil ATF.
I put a temp gauge on the TC output line (stock 2000 Nissan Xterra) and usually saw about 120 deg F over ambient in normal driving. The point of this was to understand how peak oil temperature was related to TC lockup and boy did I learn a few things.
I did a short run with my ODBII software in my BMW330Ci automatic. I believe I ran down the freeway about 5 miles and came back, total of about 12 miles.
The Trans temp started at 111F and after about 15 minutes it was at 201F.
My 07 Silverado with factory trans cooler, runs between 70 to 80 degrees above ambient when fully warmed up. Highest trans temp I`ve seen was 185.
It depends on where the gauge is located.
There are hot spots that differ widely from the coolest.
Under 200F would be my goal.
Most transmissions run too hot.
Factory tow packages are usually just adequate for normal driving.

Definitely buy the deep pan or a larger ATF cooler.
And, PH8a sized ATF filter kits add capacity, cooling, and the filtration we lack.

And, if you're up to it, many transmissions have VB mods or shift kits that will help.
If your car already has an external cooler, you do not need to put another one on, or take out the factory external cooler to put another one on.

If you have a Ford product and it has the external cooler with the thermostatic bypass, you could see if you could put a lower temp bypass on there.
On my F-150, I have a Mag Hytec deep transmission pan w/ cooling fins, and a B&M Racing Hi-Tek Automatic Transmission Cooling System w/ a 9-1/2" diameter fan. Temps are monitored with a ScanGauge II. Normal driving around town, 30 - 45 minutes of commute traffic, has temps hovering from 156 - 160. At highway speeds for 30 - 45 minutes, or longer, temp is at or about 170 - 174.

Ford now specs their automatic transmissions to run on Mercon V. Be sure that whatever ATF you use, it meets Mercon V specs, not just Mercon. Red Line makes Synthetic D4 ATF & Synthetic High-Temp ATF, both of which meet Mercon V specs. Red Line Synthetic ATF & Synthetic D6 ATF meet Mercon specs, not Mercon V specs. When in doubt, or you just want to play it safe, you can always use the Motorcraft Mercon V ATF.
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