Automotive automatic transmission temperature ?

[blacksmith37]

I am looking for typical and maximum allowable automatic transmission (oil) temperatures; specifically for a contemporary pick-up truck - 5 ratio + torque converter.

 

[Lou Scannon]

I have some trailer towing data for an 2010 F25O 6.2 I can mine to see if I have the trans temp recorded.

I forgot what I was going to say

 

[LionelHutz]

I think something around 175-200F is a good operating range and if you are pushing over about 250F accelerating/towing then you should think about a cooler and/or servicing the trans more often. Over 300F is psuing it too high, even for only short durations.

 

[SMOKEY44211]

240-250F is ideal. Has to be above 212F to boil off water condensation that may occur via vent. ------Phil

 

[patprimmer]

I like to see engine oil get a little over water boiling point at times to clean out condensation from the water left from blow by.

As there is no normal way for blow by to deposit water in the transmission, there will be very little to be dispensed. I would be concerned for the ongoing health of my transmission if ATF temps regularly got around 250F.

Regards
Pat
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[Lou Scannon]

Empirical data I have from a 2010 F250 dyno test in a simulated trailer towing drive cycle indicates that the automatic transmission oil temperature is thermostatically controlled, with a cooling cut-in temperature of around 205°F . Observed peak temperatures are <215°F.

I forgot what I was going to say

 

[belgian1776]

I regularly run 17,000 to 25,000 lbs total weight with my 99 ford dually...I am on my 2nd automatic transmission. I now run an extra trans cooler with a electric fan in addition to the factory cooler. The trans fuid is NOT run through the radiator. I also use BG brand full sythetic trans fluid. I try very hard to keep the temps below 200 degrees and normal down the hwy temp is 188 @ 70 mph with 95 degree ambient.
I think Hemi has got things exactly right in his post.
Steve

 

[patprimmer]

I agree. Hemi has it exactly right.

Also even though you might get a fluid to stand up at 250F, other components in the transmission might fail quickly if bathed in oil at those temperatures.

Regards
Pat
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[blacksmith37]

I thought the allowable temp would be higher. The base oil goes through a hydrotreater at 800F+ ; I am sure the various additives reduce the temp tolerance.Of course any tin babbitt bushings loose strength pretty fast > 350F.
When I was a boy, I worked on transmissions from the 50's, before trans coolers :They usually had "burned" clutches and bands (phenolics ?). Apparently very high temps only developed during slippage at the contact surfaces.
I was wondering about changing trans oil in my Titan at 110,000 (it has 2 factory coolers). The oil looks and smells good (because of low temp ?)

 

[Lou Scannon]

Burned clutches was definitely an issue with the Hydramatic from my 1955 Olds when it came time to rebuild it. Though the B&M kits for the original Hydro were by then no longer available, my tranny shop (Stan's in Vancouver BC) knew enough about the early Hydros to do me up a nice performance transmission. They roughened the drums for better oil expulsion on band engagement, and installed truck clutch packs, which had flat instead of waved metal disks. For my part, I raised the 1-2, 2-3 and 3-4 shift points by studying the flow diagrams and shimming the appropriate springs. It was a trial & error procedure, so I got to be pretty quick at draining the fluid, removing the shift linkage, side cover and valve body, and changing the shim.
BTW, the early Hydro was engineered not to need anything but external convective air cooling. The power path in 3rd & 4th gears was 66% mechanical, and the fluid coupling was much more efficient than a torque converter.

I forgot what I was going to say

 

[patprimmer]

I think modern automatic transmissions use some plastic components and have some internal electrical devices like solenoids. I think they are more of a problem at 250F than is the oil itself.

Regards
Pat
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[dgallup]

Solenoid valves should be capable in excess of 250F, at least 275F. Of course, they generate some heat themselves so they will be running hotter than the rest of the transmission. Their performance may be degraded a bit too because their coil resistance will be significantly higher. But that will return to normal when they cool down.

 

[bcs5274]

gaskets and seals get soft at high temps, the additives in oils bake above 230 deg f

 

[belgian1776]

Once when hunting in Idaho a friend of mine talked me into a "shortcut" over the mountain on a dirt road. I was a little over 25,000lbs at the time with all the horses, gear, feed and extra water. I had the dually in low and trans temp went up over 350 degrees. There was nowhere to pull off, nowhere to turn around, I thought we were all going to roll off the mountain and die. After that experience the trans started losing pressure bad enough at idle that it would drop into neutral at a red light. I used my programmer to up the pressure enough to get me back home to Texas.. I installed the new cooler with the new trans and no more shortcuts for me either! I take trans temp real serious now.

 

[blacksmith37]

Hemi- you remind me of the (not so) good old days. As you say, the original hydromatics had low torque conversion (like 1 :1.2) in the fluid coupling); maybe that meant not as much heat- but I don't think so. In '56 hydromatic replaced the second clutch pack with a second fliud coupling (and I think increased torque conversion in the main coupling).
The traditional "beefed" hydro used Cad Eldorado clutch packs ( 9 and 13, regular Cad were 9 and 11- If I remember right), and a steel clutch piston instead of aluminum.
Old guy quiz- What was the first auto trans to "lock up" in direct drive ?
Ans; Packard Ultramatic (about 1955), It had about a 10" dry clutch in front of the torque converter. It looked very strange when you dropped the transmission.

 

[Lou Scannon]

blacksmith, the '56 and later 4-speed Hydros were a completely different design from the '55 and earlier. IMO and most other's opinion it was an inferior design. IIRC, the two drivers for the new design were lower tunnel height, and smoother shifts.
Therefore, the fluid coupling was reduced in diameter, which probably reduced efficiency, and a small, secondary coupling was added, which served the function of a clutch pack. Instead of engaging or disengaging a clutch pack, the secondary coupling was filled or emptied of fluid, resulting in extremely smooth, extremely slow shifts. I doubt anyone ever took one of these tranmissions racing. Sounds pretty inefficient, too. I don't recall if the second design retained the mostly mechanical power path in 3rd and 4th.
The first design Hydramatic, when prepped into a B&M "Hydrostick", was the first successful automatic transmission in drag racing, and actually dominated over all other manual and auto transmissions in gasser and probably other classes of drag racing in the early '60s, until superceded by the Torqueflite and Powerglide, I believe.

I forgot what I was going to say

 

[blacksmith37]

The '56 ("Jetaway") also added a sprage- another failure source.
The guy I worked for in Chicago was one of the better Hydro builders. His story about the steel clutch piston was that the aluminum pistons would explode under a high RPM ( high pump pressure) shift with no accumulators. I had a '37 LaSalle trans- didn't believe in automatics.
Did you mean Powerflight?; I thought Powerglides were most useful as doorstops.

 

[Lou Scannon]

Chevy Powerglides are still a respected transmission for some classes of drag racing, I believe.

I forgot what I was going to say

 

[patprimmer]

A Powerglide is probably the most dominant transmission in drag racing today and I think would be used by well over 50% of contestants in classas above stock street.

Other popular choices are, the transmission the car came with and Lenco or similar with multiplate centrifugal clutches set to slip quite a lot at launch.

Regards
Pat
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