ATF Life and Operating Temperature Question...

[PaulW]

I've been doing some thinking/reading about ATF recently and came across the following info. I'm not up on the operating temps of ATs and ATF so could you guys comment on if you think this is correct?

Also what is the normal temp an auto. transmission operates at?

"At 200 degrees, the transmission fluid will last 100,000 miles

At 220 degrees, the transmission fluid will last 50,000 miles

At 240 degrees, the transmission fluid will last 10,000 miles, varnish forms.

At 260 degrees, the transmission fluid will last 5,000 miles, seals harden.

At 295 degrees, the transmission fluid will last 1,500 miles, plates slip.

At 315 degrees, the transmission fluid will last 800 miles, fluid turns to tar."

Thanks,
Paul

 

[mechtech2]

A standard in chemistry is that a chemical reaction doubles in speed for every 17F rise in temperature. This applies to the harmful breakdown of ATF.
With an auto transmission, we should use additional aftermarket coolers in series with the stock radiator cooler, and synthetic fluids which resist shearing and temperature extremes better than dino.

 

[MolaKule]

Heat is only one factor of ATF life, albeit a major factor.

Type of driving (city - highway, number of shifts per hour/day), horsepower going through transmission, vehicle weight, oil change interval, base oil and quality of additves.

 

[PaulW]

So assuming severe driving conditions here in Phoenix, AZ. High ambient air temps in stop and go traffic what type of life would you expect out of a conventional ATF? In my case I have a Hyundai Sonata V6 and a Honda Odyssey V6. I'm assuming the stock ATF used is conventional not synthetic.

 

[PT1]

What happens at 400 degrees?

 

[benjamming]

Originally Posted By: PT1
What happens at 400 degrees?


Transmission is removed and another one is installed in its place.

 

[mechtech2]

Let it cool, first.

 

[MolaKule]

PaulW,

I have offspring in Suprize and we change their ATF every two years or 20k.

 

[Donald]

This list has been posted before. As others have said, aftercooler for towing, synthetic ATF for everyone and Magnefine for everyone and you will get as much as is reasonable out of transmission.

 

[BuickGN]

It's funny looking at that chart. People over on the Acura forums thought I was wasting my time installing a cooler on a 3G TL and I drive between Phoenix, Vegas, and Bakersfield regularly during the summer.

 

[another Todd]

The transmission in my motorhome when not shifting a lot through the hills runs about 180F. Have seen it get up to about 225F. But this is just out of the converter and before the coolers-the hottest area of the trans. The sump fluid I would guess is at least 20 degrees cooler.

 

[Jim Allen]

In my former life, I went to an automatic transmission rebuild school and there was a section on lubricants. They noted the same or a similar charts as posted above on temps but also spoke about cycles. A cycle is a shift. In town the trans shifts more often than on the highway. Each time the trans shifts, it slips a little to avoid snapping your neck. Each time it slips, there are many localized temperature spikes and some shearing action. All this combines to wear out the oil even though you might not see generalized high temps, as you might measure with a gauge. In the end, they recommended that high cycle transmissions get a fluid change more often... no longer than about 30K miles. Bear in mind that this was more than 20 years ago. Oil and transmissions have improved but I think the basic advice is still good.