Automatic Transmission/Transaxle: Description and Operation

4L60E Transmission ID:

TRANSMISSION GENERAL DESCRIPTION
The HYDRA-MATIC 4L60-E is a fully automatic rear wheel drive electronically controlled transmission. It provides four forward ranges including overdrive, and reverse. Shift points are controlled by the Powertrain Control Module (PCM) via two shift solenoids. Oil pressure is supplied by a vane type oil pump, and regulated by the PCM with a transmission pressure control solenoid (force motor). Shift schedules and [1][2]Torque Converter Clutch (TCC) apply rates are also controlled by the PCM and are influenced by transmission temperature.

The transmission can be operated in any one of the following seven modes:

P - Park position prevents the vehicle from rolling either forward or backward. (For safety reasons the parking brake should be used in addition to the park position.)

R - Reverse allows the vehicle to be operated in a rearward direction.

N - Neutral allows the engine to be started and operated while driving the vehicle. If necessary this position may be selected if the engine must be restarted with the vehicle moving.

OD- Overdrive is used for all normal driving conditions. It provides four gear ratios plus converter clutch operation. Downshifts are available for safe passing by depressing the accelerator.

D - Drive position is used for city traffic and hilly terrain. It provides three gear ranges. Again, downshifts are available by depressing the accelerator.

2 - Manual second is used to provide acceleration, engine
2 - Manual second is used to provide acceleration, engine braking, or greater traction from a stop. When manual second is chosen, the vehicle will start out and remain in second gear. This range may be selected at any vehicle speed.

1 - Manual Lo is used to provide maximum engine braking. This range may also be selected at any vehicle speed.

Range Reference Chart:

TRANSMISSION COMPONENT AND SYSTEM DESCRIPTIONS
The mechanical components of this unit are:

^ Torque converter with converter clutch
^ Vane type oil pump
^ Five multiple disc clutches
^ 2-4 band assembly
^ Two planetary gear sets
^ One sprag clutch
^ One roller clutch
^ Control valve assembly

The electrical components of this unit are:
^ The PCM Located remotely from transmission inside passenger compartment.
^ Two shift solenoids
^ 3-2 downshift solenoid
^ Transmission pressure control solenoid (force motor)
^ Torque converter clutch solenoid and wiring harness assembly
^ Transmission fluid temperature sensor
^ Fluid pressure switch assembly
^ Vehicle speed sensor (2WD only)

TRANSMISSION ADAPT FUNCTION
The Hydra-matic 4L6O-E transmission uses a line pressure control system which has the ability to adapt the system's line pressure to compensate for normal wear of clutch fib& plates, seals, springs, etc. This "learning" feature is similar to what is used for fuel control (integrator/block learn).
The transmission only uses the adapt function for the 1-2 upshift. The PCM monitors engine speed to determine if the shift is occurring too fast (harsh) or too slow (soft) and adjusts the pressure control solenoid to maintain the correct shift feel. The line pressure can adapt to values ranging from 5 psi below, to 10 psi above normal line pressure.