2012 Jeep Grand Cherokee Owner Manual - Page 439

STARTING AND OPERATING 437 these conditions, using a lower gear range will improve Downshifting the transmission to the lowest possible performance and extend transmission life by reducing gear (when climbing a grade), or shifting to NEUTRAL (when stopped in heavy traffic) can help to reduce this excessive shifting and heat buildup. excess heat generation. If the transmission operating temperature exceeds normal operating limits, the powertrain controller will During cold temperatures, transmission operation may modify the transmission shift schedule and expand the be modified depending on engine and transmission range of torque converter clutch engagement. This is temperature as well as vehicle speed. This feature imdone to prevent transmission damage due to overheat- proves warm up time of the engine and transmission to achieve maximum efficiency. Engagement of both the ing. torque converter clutch and the top overdrive gear are If the transmission becomes extremely hot, the "Transinhibited until the transmission fluid is warm (refer to the mission Temperature Warning Light" may illuminate and "Note" under "Torque Converter Clutch" in this section). the transmission may downshift out of Overdrive until During extremely cold temperatures (-16°F [-27°C] or the transmission cools down. below), operation may briefly be limited to first and NOTE: Use caution when operating a heavily loaded direct gears only. Normal operation will resume once the vehicle at low speeds (such as towing a trailer up a steep transmission temperature has risen to a suitable level. 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. 5