A/T - ECVT General Information
TECHNICAL BULLETIN # 122TRANSMISSION: ECVT
SUBJECT: General Information
APPLICATION: Subaru Justy
DATE: Aug 92
SUBARU -- ECVT
CAUTION # 1
Before you accept the job of repairing or rebuilding an ECVT be advised that several special tools are required for expanding the pulleys, measuring pulley alignment, pulley endplay etc. Without these tools, proper service is at the very least extremely difficult, if not totally impossible.
CAUTION # 2
The ECVT transmission works on totally different principles as compared to conventional automatic transmissions. This transmission uses an electromagnetic powder clutch instead of a torque converter. An electric current is induced into the powder clutch causing it to transmit engine torque to the transmission.
Instead of using planetary gear sets, bands, and clutches, this transmission uses a set of hydraulically controlled variable diameter pulleys and a steel belt for ratio changes.
To a technician who is not familiar with this transmission operation, a test drive will reveal what may be interpreted as slipping or characteristics usually associated with vehicles equipped with very high stall speed converters.
The ECVT is capable of an infinite number of ratios between 2.5:1 and .5:1. The ratio change is very gradual and smooth which results in a shiftless transmission.
In the words of one technical writer, "If you think of a conventional automatic as a three-way light switch, the ECVT operates like a dimmer control.
ELECTROMAGNETIC POWDER CLUTCH SERVICE INFORMATION
Removing the starter will allow access to the brush holder. Remove the brush holder to check for wear, contamination etc.
The wear limit indicator is the scribed mark on the brushes. The brushes must not be contaminated with oil.
BEARING: New brush holder # 30510KA040.
Check the bearing for seizure, wear, noise or improper rotation.
The bearing must run smoothly, without any signs of rough spots.
Always handle the powder clutch carefully to avoid damage to the slip rings. Clean the slip rings with a soft cloth and electrical contact cleaner, brake cleaner, etc. Install the brush holder only after the engine transmission and powder clutch are bolted together as an assembly.
CONTINUITY CHECK:
Measure the resistance between the slip rings using an ohmmeter. If it is 2 to 4 ohms the slip rings are functioning properly.
If continuity does not exist, or resistance is extremely low, replace the clutch.
INSULATION CHECK:
Check insulation resistance between each slip ring and aluminum bracket of the electromagnetic powder clutch using an ohmmeter (set in the max. ohm range). If continuity exists, replace the electromagnetic powder clutch.
Do not attach the test probes to the slip rings with alligator clips as this may scratch them.
Use an ammeter in series with the brush feed wires to monitor clutch current.
The rated current applied to the coil in the clutch is divided into three steps, determined by how far the accelerator pedal is depressed, and road speed.
Accelerator pedal released 0.4-1.8 A *
Accelerator pedal pressed lightly 3.0 A **
Accelerator pedal pressed heavily 3.51 A ***
* Above preset road speed.
** Only accelerator switch operated and above preset road speed.
*** Accelerator switch and throttle position switch operated, above preset road speed.
If you are bench checking the powder clutch it should hold 105 ft/lbs of torque when 3.5 amps is induced into the coil.
HANDLING PRECAUTIONS
1. Do not turn the powder clutch over. Always store it with the hub up or the powder may spill out of the opening.
2. Do not scratch or dent the slip rings.
3. Do not attempt to dis-assemble the powder clutch. No internal parts are serviceable. The powder clutch is serviced as an assembly only.
4. Do not steam clean or wash the powder clutch in a solvent tank as this will contaminate the powder inside.
5. Do not remove the drive plate from the engine as it is properly balanced with the flywheel.
BELT HANDLING PRECAUTIONS
Before you attempt to separate the case halves be sure to first remove the pump and rotate the pitot tube from the 9 O'clock position, to the 12 O'clock position to prevent damaging the pitot tube.
When re-assembling the unit, place the rear case half over the pulley's with the pitot tube in the 12 O'clock position. Once the case halves are assembled, rotate the pitot tube back to the 9 O'clock position, before installing the pump.
BELT HANDLING PRECAUTIONS
The belt is made up of 280 individual segments and 10 steel bands. Special care must be exercised when handling the belt to prevent accidental dis-assembly of the belt.
Install tie-raps on the belt before attempting to remove it from the pulley.
Always store the belt with the tie-raps on. Never remove the tie-raps until AFTER it is installed on the pulleys.
The belt is direction sensitive. It must face the direction shown.
ACCELERATOR SWITCH AND THROTTLE POSITION SWITCH
There are 2 switches activated by the accelerator pedal which inform the computer of throttle opening. The adjustment and operation of these switches is critical for proper transmission operation. Both switches are normally closed, and open when the accelerator is depressed the specified amount.