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Automatic Transmissions
OIL TEMPERATURE MEASURED AT CONVERTER OUTLET
TO COOLER:
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300°
F=
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The
maximum allowable temperature. This is the recommended place to install a
temperature gauge or sensor. Do not allow the converter outlet temperature
to exceed 300°
F. The temperature at this location will vary significantly because of
load, hill climbing, etceteras. If the temperature reaches 300° F, reduce throttle. To lower
transmission temperature with transmission in neutral, run the engine at
1,200 RPM for at least 2 - 3 minutes while keeping a close check for signs
of engine overheating. A transmission in a heavy throttle, stall condition
(a typical situation is rocking a vehicle stuck in mud, sand, or snow),
may increase temperature at a rate of 1°
degree per second of stall.
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OIL TEMPERATURE MEASURED AT OIL PAN OR SUMP:
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150°
F=
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The
minimum operating temperature. Note: It is possible in low ambient
temperatures to overcool the transmission with auxiliary oil to air
coolers. Oil to water coolers in standard factory radiators will normally
not overcool a transmission.
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175-200°
F=
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Normal
pan oil temperature operating range.
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275°
F=
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Maximum
allowable oil pan temperature for short durations during long hill climbs.
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300°
F=
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Damage
occurs to internal transmission parts, including warpage of metal parts,
degradation of clutches, and melting of seals. Transmission oil oxidizes,
(forming varnish-like substances causing further clutch slippage and
compounding heat build up) and transmission oil life is extremely short.
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AUTOMATIC TRANSMISSION FLUID LIFE /
TEMPERATURE RELATIONSHIP:
Automatic
transmission oil can provide up to 100,000 miles of service before oxidation
requires replacement, at an operating temperature of 175°
F. Above this temperature, the oil oxidation rate doubles with each 20°
degrees F increase in oil temperature. See chart.
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DEGREES
F
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MILES
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DEGREES
F
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MILES
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175
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100,000
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295
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1,500
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195
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50,000
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315
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750
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215
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25,000
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335
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325
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235
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12,500
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355
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160
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255
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6,250
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375
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80
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275
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3,125
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395
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40
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Note:
Transmission oil and filter should always be changed more frequently when
driving with heavy loads (RVs), typically at least every 25,000 mile intervals,
since converter outlet temperatures then normally far exceed the ideal 175°
F.
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