DESCRIPTION AND OPERATION
45RFE AUTOMATIC TRANSMISSION
DESCRIPTION
The 45RFE automatic transmission is a sophisti-
cated, multi-range, electronically controlled transmis-
sion
which
combines
optimized
gear
ratios
for
responsive performance, state of the art efficiency
features and low NVH. Other features include driver
adaptive shifting and three planetary gear sets to
provide wide ratio capability with precise ratio steps
for optimum driveability. The three planetary gear
sets also make available a unique alternate second
gear ratio. The primary 2nd gear ratio fits between
1st and 3rd gears for normal through-gear accelera-
tions. The alternate second gear ratio (2 prime)
allows smoother 4–2 kickdowns at high speeds to
provide 2nd gear passing performance over a wider
highway cruising range.
The hydraulic portion of the transmission consists
of the transmission fluid, fluid passages, hydraulic
valves, and various line pressure control components.
The primary mechanical components of the trans-
mission consist of the following:
• Three multiple disc input clutches
• Three multiple disc holding clutches
• Five hydraulic accumulators
• Three planetary gear sets
• Dual Stage Hydraulic oil pump
• Valve body
• Solenoid pack
The TCM is the “heart” or “brain” of the electronic
control system and relies on information from vari-
ous direct and indirect inputs (sensors, switches, etc.)
to determine driver demand and vehicle operating
conditions. With this information, the TCM can cal-
culate and perform timely and quality shifts through
various output or control devices (solenoid pack,
transmission control relay, etc.).
TRANSMISSION IDENTIFICATION
Transmission identification numbers are stamped
on the left side of the case just above the oil pan gas-
ket surface (Fig. 1). Refer to this information when
ordering replacement parts. A label is attached to the
transmission case above the stamped numbers. The
label gives additional information which may also be
necessary for identification purposes.
GEAR RATIOS
The 45RFE gear ratios are:
1st . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.00:1
2nd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.67:1
2nd Prime . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.50:1
3rd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.00:1
4th . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.75:1
Reverse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.00:1
OPERATION
The 45RFE offers full electronic control of all auto-
matic up and downshifts, and features real-time
adaptive closed-loop shift and pressure control. Elec-
tronic shift and torque converter clutch controls help
protect the transmission from damage due to high
temperatures, which can occur under severe operat-
ing conditions. By altering shift schedules, line pres-
sure, and converter clutch control, these controls
reduce heat generation and increase transmission
cooling.
To help reduce efficiency-robbing parasitic losses,
the transmission includes a dual-stage transmission
fluid pump with electronic output pressure control.
Under most driving conditions, pump output pres-
sure greatly exceeds that which is needed to keep the
clutches applied. The 45RFE pump-pressure control
system monitors input torque and adjusts the pump
pressure accordingly. The primary stage of the pump
works continuously; the second stage is bypassed
when demand is low. The control system also moni-
tors input and output speed and, if incipient clutch
slip is observed, the pressure control solenoid duty
cycle is varied, increasing pressure in proportion to
demand.
Fig. 1 Transmission Part And Serial Number
Location
21 - 182
45RFE AUTOMATIC TRANSMISSION
WJ