Transmission

• Info
  • Multiplies torque. Multiplication range = 1.8 – 2.5. You might say the stator supercharges the pump.
  • https://youtu.be/bRcDvCj_JPs?t=368

• Slipping Stator Clutch
  • The stator in being able to move backwards allows the out flow to end up being directed back at itself. That is surely the reason for the greatly reduced stall speed and poor output power to the transmission input shaft. (Dennis from Automatic Transmission Rebuilders Association)
  • In an event of a freewheeling stator, the stator cannot redirect the fluid resulting in little to no acceleration of the vehicle. (U.S. Army TARDEC Fuels and Lubricants Research Facility)
    • Case Study. 2010 SsangYong Kyron (with Benz System)
      • Car doesn’t move uphill from a standstill at all. On a flat ground, there is a power lag, then picks up and drives like normal.
        • If it were an engine performance problem then accelerating after decelerating from 50 mph to 30 mph would show a performance problem too.
        • The description of the problem sounds like what happens when the stator one-way clutch fails and the stator is no longer redirecting the fluid at initial acceleration so the torque multiplication that normally happens at take off isn’t happening. This stator one-way clutch failure will make for poor acceleration from a stop, slightly sluggish slow speed acceleration and normal feeling acceleration at all other speeds.
• Seized Stator Clutch
  • Seized stator clutches (no overrun) can cause the engine to labor big time approaching coupling point.

Lockup Clutch (TCC)

• The engagement of this clutch causes the engine to lock to the transmission input shaft thereby leading to a direct 1:1 drive ratio.
  • The Lockup Solenoid duty cycle should go to 0 percent when the Throttle Position Sensor is above 40 percent and should return to 100 percent when the throttle is returned back to 15 to 20 percent.
  • The Lockup Solenoid duty cycle should go to 0 percent whenever the brake pedal is applied, regardless of speed.
  • The duty cycle should go to 0 percent whenever the throttle is fully released and the vehicle has decelerated below 30 MPH.

Tests

Scan Tool Test

• Monitor the Converter RPM (Slip) and compare that to Input Shaft speed RPM at greater than 45 MPH on a smooth, flat surface after the vehicle is warmed up and the fuel system is in a closed loop.
• Monitor how the Converter Lockup Solenoid responds to an increased amount of throttle.
  • The Lockup Solenoid duty cycle should go to 0 percent whenever the brake pedal is applied, regardless of speed.
  • The duty cycle should go to 0 percent whenever the throttle is fully released and the vehicle has decelerated below 30 MPH.
  • The Lockup Solenoid duty cycle should go to 0 percent when the Throttle Position Sensor is above 40 percent and should return to 100 percent when the throttle is returned back to 15 to 20 percent.
• When looking at the Toque Converter RPM versus the Input Shaft RPM, observe if the scan tool data has a Converter Slip Speed PID.
  • If the Lockup System is functioning correctly, the Slip Speed value should never be above 50 RPM. Try gently depressing the throttle on a gradual incline above 45 mph. When doing this, the Slip Speed should not increase. If it does and the Lockup Solenoid duty cycle is 100 percent—meaning it is fully applying the converter clutch—then you know you have a slipping Converter Clutch.
  • If the Slip Speed stays steady but the transmission Output Shaft Speed starts to decrease (along with the MPH), then you know that you have an internally slipping transmission, usually caused by worn Clutch Packs or Sprag 1-Way clutches.
  • If the Slip Speed remains very high and the Lockup duty cycle is 100 percent, then it is likely that the Solenoid, Wiring, or PCM is defective, because the duty cycle is reporting that the PCM is commanding the Lockup System to apply, but there is no change. Even with worn out Converter Clutches, there is always some kind of Slip Speed reading. It may go very high whenever the throttle is applied, but there should be some kind of a RPM reduction between the Converter Speed and the Input Shaft speed that verifies the Lockup Solenoid and PCM are trying to do their jobs.

Stall Test

• Drive the vehicle until normal operating temperature is achieved.
• Check the stall speed specifications, for your vehicle.
• Firmly press brakes and depress accelerator pedal to the floor.
• Observe the maximum engine speed (rpm). This is a stall speed.
  • If the rpm is higher than specifications, a holding clutch or band is slipping.
  • If the rpm is lower than specifications, the torque converter is defective (one way clutch or stator is slipping) or the engine is not producing normal output.

RPM Test

• Drive on the steady cruise about 50MPH.
• While maintaining constant speed with your right foot on accelerator, gently apply brake pedal with your left foot to open electrical circuit for the TCC through the brake switch.
• TCC will disengage and the RPM should increase about 150 to 250 rpm and then drop back when the brake pedal is released. This RPM change is your proof that TCC is working.