Assumptions:
The automatic is in good, functional condition and has been serviced
regularly.
An ATF temperature gage is installed in the line to the cooler as DickJ
suggested.
The design is not a piece of junk like the TH-200.
It is being used on fairly surfaces, not the Rincon Trail.
Facts:
98% of the heat in ATF comes from the Torque Converter when it is Torque
Converting.
Petroleum ATF starts degrading at a bit less that 300 degrees.
PAO Synthetics like Mobil1 , Amzoil and a few others, at above 425 degrees.
Modern Automatic soft parts can tolerate 350 degrees.
A Torque Converter is a simple "Fluid Coupling" above a certain RPM,
primarily
determined by stall speed and engine torque curve. For large production
road cars
and trucks, 2500-3500 RPM. Above this RPM it generates about 4-6% of the
heat
going into the ATF.
Plan: keep ATF at a safe temperature.
How:
A) Stop heating the oil.
B) Remove all excess heat as needed.
A) It's easy with modern automatics, the driver does it. (cheap)
If the automatic has a converter clutch, the driver is home free.
All he needs to do is operate the shift lever to keep the RPM
up high enough so that the clutch is always engaged.
Clutch engaged = no torque converter = no heat.
If it's an older unit, you do the same thing but you need to watch the
tach to KEEP engine RPM high enough to always operate the converter
in it's "Fluid Coupling" mode.
I used this method with my 1965 Dodge A-100 truck (A-747). After 35 years
and 187,000 miles I gave it to a friend. It needed new soft parts but worked
fine if you let it run for a few minutes if it had been setting for a
few days.
The only parts that were replaced were the front oil seal when I
re-installed
the engine and 3 or 4 filters.
Note: I would always use petroleum ATF in an untested, by you and your
application, transmission. A clutch (or band) can slip because of a defect
and, for a few seconds heat to over 300 degrees in spots. You won't notice
it, but it will fry a small bit of petroleum ATF. You can detect this on
the
dipstick with your nose. If it's Real PAO Synthetic (Mobile1, etc.) the
heat
won't bother it and it will smell perfect. Not good.
Continued in part 2
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