Fri 25 May 2007

42RE TRANSMISSION
TRANSMISSION GEAR RATIOS
Gear ratios are:
 1st 2.74:1
 2nd 1.54:1
 3rd 1.00:1
 4th 0.69:1
 Rev. 2.21

The 42RE is a four speed fully automatic transmission
(Fig. 1) with an electronic governor. First
through third gear ranges are provided by the
clutches, bands, overrunning clutch, and planetary
gear sets in the transmission. Fourth gear range is
provided by the overdrive unit that contains an overdrive
clutch, direct clutch, planetary gear set, and
overrunning clutch. The overdrive clutch is applied in
fourth gear only. The direct clutch is applied in all
ranges except fourth gear. The 42RE is equipped
with a lock-up clutch in the torque converter.

45RFE AUTOMATIC TRANSMISSION
TRANSMISSION GEAR RATIOS
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

The 45RFE automatic transmission is a sophisticated,
multi-range, electronically controlled transmission
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
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 accelerations.
The alternate second gear ratio (2prime) allows
smoother 4.2 kickdowns at high speeds to provide
2nd gear passing performance over a wider highway
cruising range.
The 45RFE offers full electronic control of all automatic
up and downshifts, and features real-time
adaptive closed-loop shift and pressure control. Electronic
shift and torque converter clutch controls help
protect the transmission from damage due to high
temperatures, which can occur under severe operating
conditions. By altering shift schedules, line pressure,
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 pressure
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 monitors
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.
A high-travel torque converter damper assembly
allow earlier torque converter clutch engagement to
reduce slippage. Needle-type thrust bearings reduce
internal friction. The 45RFE is packaged in a onepiece
die-cast aluminum case. To reduce NVH, the
case has high lateral, vertical and torsional stiffness.
It is also designed to maximize the benefit of the
structural dust cover that connects the bottom of the
bell housing to the engine bedplate, enhancing overall
power train stiffness. Dual filters protect the
pump and other components. A pump return filter is
added to the customary main sump filter. Independent
lubrication and cooler circuits assure ample
pressure for normal transmission operation even if
the cooler is obstructed or the fluid cannot flow due
to extremely low temperatures.

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