fluid temp versus transmission life expectancy

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From the life automotive products website. Interesting reading.
http://www.lifeautomotive.com/technicaltips/default.asp#3
From what I gather , take the temperature of your transmission fluid at operating temp and you can determine the transmission life expectancy. I would see this very useful when buying a used car or checking if it is worth changing fluid in an older trans.
I would use a non contact thermometer on the pan. Fast, clean and cheap.

Fluid Temp VS. Transmission Life Expectancy

175°F = 100,000+ miles
190°F = 90,000 miles
210°F = 55,000 miles (Pressure Drops)
230°F = 25,000 miles (Valves Stick)
250°F = 17,000 miles (Varnish Forms)
270°F = 4000 miles (Seals & Clutches Burn)
300°F + = TRANSMISSION FAILURE
 
That doesn't make much sense though. My car runs the transmission cooler lines through the radiator for cooling. The coolant temperature is controlled at 190ºF via the thermostat.

According to this chart, the transmission temperature is going to naturally run much higher than 175ºF yet I've never EVER had a transmission fail prior to 100,000 miles of use.

Is this website trying to sell a additive? I notice on the bottles of Lubegard they have the same sort of chart.
 
Well most modern transmission are electronically controlled now a days. Most have adaptive logic (whatever you want to call it) to allow the transmissions to change shift patterns to keep themselves cool. Also torque converter lock up will allow the fluid to cool as well with the mechanically coupling.

If you watch your transmission temps (my Regal for example) the temperature is always below ECT. Unless I am at the track or something of course.

I believe aux transmission coolers have their place just not for most vehicles anymore.
 
Those charts are somewhat misleading because they illustrate oil life at a constant temp.... BUT.... your actual trans temp is never constant. The basic rule is that it's time at temp that kills the oil, so based on temps alone, it's very difficult to plot in such a black and white fashion when the temps are constantly changing. The temp numbers change seasonally as well as by load, driving style, etc.

I can monitor trans temp on my Ford truck in three places (cooler oil pan and valve body) and have had gauge setups on a couple of other trucks over the past 20 years as well. The cooler out line can be 225 while the converter is unlocked but the pan is still at 160F. The converter locks up and the cooler out line drops to 180. It takes a while to heat the trans up, too, so on short hops, you may never even reach 140F. If you had a computer that could plot all the high spots as you drove, I image you could predict fluid life by that but other wise, IMO, those charts are a rough guideline at best.

Given the minimal filtration most trannies have, I worry more about that. Most tranny fluids will (or should) be condemned for it's contaminant load long before it would be condemned for oxidation. That statement is backed up by some 25 year long studies on trans fluids by a couple of engineers named Eleftherakis and Khalil (google them).
 
agreed. plus the radiator never really sits at 190° either unless it's quite undersized.

I had a minivan with trans temp gauge installed in cooler inlet (heated fluid straight from trans). Needed 45+ minutes of driving before it'd come off 120°. It could spike fast on a hill climb, and generally after an hour began to average 160°.

I *really* liked having an aftermarket trans temp gauge. Learned more in a week about trans behavior than in years...

M
 
I fully agree with this statement. Transmission temperature never stays constant. I have IR thermometer I use to check the pan temperature and it depends a great deal on the season and driving style. Highway trips in the winter at 70 mph - temperature never goes above 150F. In the summer is is about 170F at 70 mph. In stop and go traffic with heavy accelerations I've seen it as high as 190F. Same was in the mountains in the summer time. This is for Toyota corolla transmission.
 
My Tacoma's tranny sees temps barely 100 degrees during the winter. During the summer as high as 170 degrees. I do have a secondary cooler.
 
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