Sorry for the copy and paste job but I thought this would help
545RFE Transmission Operation
The Transmission Control Module (TCM) is programmed to allow a select variety of shift schedules that are dependent on the following physical conditions:
· Selected gear range
· Throttle position
· Engine load
· Transmission fluid temperature
· TCM software level
The TCM will adjust the shift schedule of the transmission as environmental and driving conditions change.
-16°F and below and with the transmission in the Drive position, the shift sequence will be 1st to 3rd until the ATF temperature reaches -12°F. When placing the gear selector in either 1st or 2nd gear the transmission will be on 2nd gear only. There will be no torque converter lock up and switching off Overdrive will have no effect.
-12°F and -10°F the transmission shift sequences are as follows:
· No torque converter lock up
· No shift in to 5th gear
· Delayed 2-3 upshifts
· Delayed 3-4 upshifts
· High speed 4-2, 3-2, or 2-1 kickdown shifts are prevented
· High throttle opening shifts will be early
· Switching off Overdrive will prevent shifts into 4th gear
-10°F and 36°F the transmission shift sequences are the same as above, except that 2-3 upshifts are not delayed. Switching off Overdrive will prevent shifts into 4th gear
40°F and 80°F All shift sequences are normal except there will be no torque converter lockup. Switching off Overdrive will prevent shifts into 5th gear.
80°F and 240°F This is normal operating fluid temperature. The 545RFE will be in the normal shift sequence, including allowing torque converter lockup.
240°F ATF or the engine coolant 244° F, the transmission shift sequences will be as follows:
· delayed 2-3 upshift
· delayed 3-4 upshift
· 3rd gear FEMCC from 30-40 MPH
· 3rd gear PEMCC above 35 MPH
· Above 25 MPH the torque converter will not unlock unless the throttle is closed or if a wide open throttle, 2nd gear PEMCC to 1 kickdown is made.