Subaru LEGACY 2002 Quick Reference Index page 312

Automatic Transmission
L: AWD CENTER DIFFERENTIAL CONTROL (VTD MODELS)
1. CONTROL DESCRIPTION
The TCM controls the engagement of the center differential's multi-plate clutch (LSD) using maps
that are pre-programmed based on the throttle opening and engine speed. It selects a map ac-
cording to driving conditions and use it as the control basis.
2. ORDINARY CONTROL
The torque input to the multi-plate clutch is calculated according to various factors such as intake
manifold pressure, torque converter turbine speed and selected speed gear. Based on the calcu-
lation result, the basic coupling force of the clutch is determined.
The basic coupling force thus obtained is then corrected according to the road slipperiness (which
is determined based on steering angle, yaw rate, lateral G signals from the VDC control module)
and the feedback correction factor which is used for making the actual yaw rate agree with the yaw-
rate estimated from the steering angle sensor signals.
3. START CONTROL
When the vehicle speed is 0 km/h (0 MPH), the TCM makes control to generate differential action
limiting torque that is proportional to the throttle angle.
This enables the vehicle to start smoothly without swerving even on a slippery road.
4. TURNING CONTROL
The TCM makes a correction such that the input torque to the multi-plate clutch is reduced as the
steering angle increases.
This function is performed to improves turning performance at certain vehicle speed range.
5. SLIP CONTROL
When front or rear wheels start slipping with the vehicle running slower than the predetermined
speed, the TCM makes control to increase the differential action limiting torque.
This function maintains traction and improves driving stability.
TRANSMISSION CONTROL MODULE (TCM)
Control
in turns
AT-36
B3H1652B