Jeep Grand Cherokee Owner's Manual page 446

444 STARTING AND OPERATING
these conditions, using a lower gear range will improve
performance and extend transmission life by reducing
excessive shifting and heat buildup.
If the transmission operating temperature exceeds nor-
mal operating limits, the powertrain controller will
modify the transmission shift schedule and expand the
range of torque converter clutch engagement. This is
done to prevent transmission damage due to overheat-
ing.
If the transmission becomes extremely hot, the "Trans-
mission Temperature Warning Light" may illuminate and
the transmission may downshift out of Overdrive until
the transmission cools down.
NOTE: Use caution when operating a heavily loaded
vehicle at low speeds (such as towing a trailer up a steep
grade, or in stop-and-go traffic) during hot weather. In
these conditions, torque converter slip can impose a
significant additional heat load on the cooling system.
Downshifting the transmission to the lowest possible
gear (when climbing a grade), or shifting to NEUTRAL
(when stopped in heavy traffic) can help to reduce this
excess heat generation.
During cold temperatures, transmission operation may
be modified depending on engine and transmission
temperature as well as vehicle speed. This feature im-
proves warm up time of the engine and transmission to
achieve maximum efficiency. Engagement of both the
torque converter clutch and the top overdrive gear are
inhibited until the transmission fluid is warm (refer to the
"Note" under "Torque Converter Clutch" in this section).
During extremely cold temperatures (-16°F [-27°C] or
below), operation may briefly be limited to first and
direct gears only. Normal operation will resume once the
transmission temperature has risen to a suitable level.