Jim Lane

How hot is too hot, and this is without a load.

I finally got my Transmission Temperature Gauge connected the other day and I am kind of shocked about how hot it is running.

I took it out tonight and driving around in light traffic or at a stop light it is running between 160* - 180*



But as soon as I leave the stop the temperature starts to rise, a quick jump with heavy throttle (not WOT) will quickly bury the pointer past 250* in seconds flat.

My Autometer electric sender is in the hot line about 6" from the outlet of the transmission and the response to the temperature rise seems almost instantaneous.

I am concerned that I might be driving through my new torque converter generating lots of extra heat.

This new transmission is less than 6 months old and the ATF is not bright red as I think it should be with this few miles on it.

And since my gauge only goes to 250* I have no idea how hot it is really getting and it appears from all of the data I can find on line that I am already cooking my ATF.

I did take a quick jump on the freeway and accelerating up to 75MPH the trans temp hit 250* and then started backing down to around 200* but by then I was already out of the throttle and I have a LOT of air flowing through my coolers


ATF Temp Chart
from http://www.niehoff.com/techtips/techtipidx.html

new 4/21/01


--------------------------------------------------------------------------------
Automatic Transmission Fluid Oxidation
Automatic transmission fluid will provide 100,000 miles of service before oxidation occurs under normal operating temperatures of about 170°F. Above normal operating temperatures, the oxidation rate doubles (useful life of fluid is cut in half) with each 20° increase in temperature.

The approximate life expectancy at various temperatures is as follows:


175°F 100,000 miles
195°F 50,000 miles
212°F 25,000 miles
235°F 12,000 miles
255°F 6,250 miles
275°F 3,000 miles
295°F 1,500 miles
315°F 750 miles
335°F 325 miles
355°F 160 miles
375°F 80 miles
390°F 40 miles
415°F Less than 30 minutes


This information clearly shows why transmission oil coolers and the various maintenance intervals are recommended for severe usage.

Above 300°F, the metals inside the transmission will warp and distort in varying degrees depending on the severity of overheat. Because this damage occurs and fluid life is so seriously impaired, rocking out of snow, mud or sand should never exceed a very few minutes.

Here is how my oil cooler circuit is set up,

That leak was driving me nuts, turned out to be a crack in the fitting I am going to replace this when I get a replacement hot line.



Hot ATF from the transmission makes its first stop at my new refurbished under bed cooler, hot ATF enters the AUX cooler first.

This is rated at 29,200 BTU and has the factory fan cooling it (I am thinking about stacking another 29,200 BTU unit under this one in the same ducted air stream for a 58,400 BTU cooler package.



Then from the cooler the ATF enters the filter where it is cleaned before it heads back to its original route into the heat exchanger on the side of the engine.



All of the brackets will come off, cleaned and painted.

This a NAPA #1515 filter,
I hope filtering the ATF with this filter will keep the transmission cleaner the the paper filter in there now, also it will be a lot easier to replace it.



Here you see now how easy it is to service the filter on my transmission.
Yes the oil leak made a real mess of the under side of my truck, but after 2 gallons of Zep Orange Citrus Cleaner and a spray bottle it is almost clean again.



So what do you think about the ATF temperature, and the not so red fluid?
I had also turned my fuel down 1/2 turn about 6 months ago when the trans was going out but it still exploded.

I am taking the truck back to the transmission shop probably next week.


Jim

bannerd

Wow, that should be lower than that, 140 is about normal if you calculate the current temperature outside. I would be very careful even around 220F.

YOREL

A couple of thoughts. I am also in the process of installing an auxiliary cooler and spin on filter; however, I am going to eliminate the OEM fluid to fluid cooler as it sprung a leak and contaminated a freshly rebuilt tranny with less than 200 miles and took out the forward clutch pack. There has been considerable discussion regarding this and I am going to take my chances as I can not justify the replacement cost of the F2F cooler or its susceptibility to leaking. The F2F cooler will always maintain the tranny fluid at around 180* as that is what the engine is operating at. In your setup maybe the fluid should exit the tranny into the F2F cooler first then through the auxiliary and filter and back to the tranny. You could also incorporate a second temp sending unit, (one on the out line and one on the return line), using the same gauge and a SPDT switch to get a better feel of what is really happening with your coolers.

peckens

i have always been curious what the effects would be of running a higher quality atf such as royal purple
From royal purple's product catolog
Max ATF is a synthetic, high performance, automatic
transmission fluid. Its high film strength helps to
dramatically reduce heat and wear.
Automatic transmissions generate a great deal of heat
and depend on the transmission fluid for cooling and
protection. More than 90 percent of all automatic
transmission failures are caused by overheating. A 20˚F
reduction in fluid temperature can double the life of the
transmission (Source: Perma Industries Inc.). Max ATF
significantly reduces heat to extend the life of your
transmission.


Max ATF is fully compatible and can be mixed with other
automatic transmission fluids; however, for the best
results drain or flush the current oil and then fill with
Max ATF.

Viscosity
cSt @ 40˚C 35.0
cSt @ 100˚C 7.5
SUS @ 100˚F 177
SUS @ 210˚F 50
@ -10˚C (14˚F) 400
@ -20˚C (-4˚F) 900
@ -30˚C (-22˚F) 2300
@ -40˚C (-40˚F) 7150
Viscosity Index 180
Flash ˚F 440
Fire ˚F 475
Pour ˚F <-69
Density
Specific Gravity @60˚F 0.84
Pounds/Gallon 6.96

On the other hand, amsoil claims their product lasts twice as long as conventional in their high temp test.

rebal

some guys will put the probe on the hot line coming right out of the converter like yours that is what kind of temps you will see, what your not seeing is how cool the oil is in the pan. I moved mine to the pan long ago because I was seeing temps like that too I since have moved it to the pan and it stayed at 140* to 180* I have just installed 2 Derale 15960 coolers and removed the heat exchanger but left the factory trans cooler up front (3 coolers total) to try and get rid of the extra heat in the radiator in summer when i tow.so far everything is working out ok I thought my trans might not warm up in the winter but its doing ok too .Its been 28* +- the last few weeks and after just a few min. of letting the engine warm up i can feel the two coolers and there warm so the trans is warming up just sitting .the fans on the 2 Derale coolers have yet to come on .but im sure this summer when its 105* out that wont be the case but so far the trans only sees 140* anymore .I have towed a 20,000 lbs gooseneck and the temps stay low but I havent made a pull in to the mountains yet or seen 100*+ temps outside. I also run amsoil ATF. its supposed to be able to take more heat and have
a longer life

bannerd

I see a autozone.

MARF75

I say F2F first also

deanhinsley1963

Jim I have mine in the hot line to and see temps of 200-220 in the summer when its very hot 95+. Yours sounds high to me. And the brown fluid does'nt sound right. Smell it and see if its burnt smelling. Those temps I quoted were for the truck empty no load. But this time of year with temps in the 40-50 range it runs around 160.

deanhinsley1963

Also forgot to mention I dont have the under the bed cooler.

NE frmhnd

Quick check of your fluid- wipe the dipstick off with a white cloth or paper towel. If he smudge is all pink, you're good. If it's brown in the middle, it's toast.

TIMMY22

I wonder if the flow rate is restricted due to smaller line, longer run, elbows, filters etc? Amount of cooling in direct proportion to flow rate BTU/liter?

In other words, a 10L/minute flow rate w/ 1 small cooler is going to remove the same BTU as a 5L/minute flow rate w/2 small coolers?

gorms

Jim what type/stall converter are you running? When I was seeing temps rise that quickly empty I needed a rebuild within a year. Also you know what pressure is on the cooler lines, I wouldn't want that spin on filter to restrict any flow. Just a thought.

TIMMY22

"This is rated at 29,200 BTU and has the factory fan cooling it "I am thinking about stacking another 29,200 BTU unit under this one in the same ducted air stream for a 58,400 BTU cooler package."

Will the second cooler be able to remove the same BTU as the first in it's discharge air? I'm guessing half? 15,000 BTU

Jim Lane

I have the hot ATF going to the axillary cooler first because that was the way it came from the dealer installed option, the idea was to super cool the ATF before it get to the hot coolant of the heat exchanger, with the fan running it has to be extracting a sizable amount of heat, you can feel the heat blowing out from under the bed when it is running.

I am not sure how many CFM the under-bed fan is but with it running I can toss a wadded up sheet of newspaper under it and it will suck it up and hold it there.

All of the hoses are 1/2" ID (actually measured as 9/16" ID) and the only 90* turns are on top of the filter head, I have plans to get a pair of radiused fittings to replace them.
I removed the dealer installer (I thought to be a restriction) 90* from the hot line and replaced it with a 1/2" ID cavity to house the temp probe.

#1515 Filter Specs.

Style: Spin-On Lube Filter
Service: Lube
Type: Full Flow
Media: Paper/Glass
Height: 5.178
Outer Diameter: 3.660
Thread Size: 3/4-16
By-Pass Valve Setting-PSI: 8-11
Anti-Drain Back Valve: Yes
Ends: Metal
Beta Ratio: 2/20=13/23
Burst Pressure-PSI: 290
Max Flow Rate: 7-9 GPM
Nominal Micron Rating: 21"

This is also the same filter used on almost all aftermarket transmission filter kits.

One thing I did notice was when the transmission was on the bench I noticed although the cooler lines are 1/2" OD x 3/8" ID the passage through the female flare adapter was either 5/16" or maybe even 1/4".

I think it has something to do with the torque converter although it is supposed to be a heavy duty diesel unit, maybe just not the correct stall, I had made the comment before that it feels like my new transmission was eating my power, it just didn't feel right.

Before, build some boost and the truck would slide the front tires on concrete.

Jim

Jim Lane

No idea what the stall rate is, I do not have a tach so I cannot check it, but I always felt it just wasn't right.

Not sure how they built this one but I would think even from having 3.07 to 3.54 would have a different stall, makes sense to me.

I do not know what the line pressure is on my trans but the shop said it can be up to 150+ PSI

I wouldn't want that spin on filter to restrict any flow. Just a thought

We used to run smaller Ph-30 full flow filters on the cooling circuits of V-730 Turbo Hydromatic Transmissions behind 8-V71 & 8V-92 series Detroit's on transit coaches.

Jim