Upshift Control and Torque Converter Clutch (TCC) Apply
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The PCM calculates the upshift points based primarily on two inputs: throttle angle and vehicle speed. When the PCM determines that conditions are met for a shift to occur, the PCM commands the shift by closing or opening the ground circuit for the appropriate solenoid.
Perform the following steps:
- Refer to Shift Speed and choose a throttle position of 10 percent, 25 percent or 50 percent. All throttle angles shown should be tested to cover the normal driving range.
- Monitor the following scan tool parameters:
- Throttle angle
- Vehicle speed
- Engine speed
- Output shaft speed
- Commanded gear
- Slip speed
- Solenoid states
- Place the gear selector in the OVERDRIVE position.
- Accelerate the vehicle using the chosen throttle angle. Hold the throttle steady.
- As the transmission upshifts, note the vehicle speed when the shift occurs for each gear change. There should be a noticeable shift feel or engine speed change within 1-2 seconds of the commanded gear change.
- Compare the shift speeds to the Shift Speed table. Refer to Shift Speed
. Shift speeds may vary slightly due to transmission fluid temperature or hydraulic delays in responding to electronic controls.
- Note any harsh, soft or delayed shifts or slipping.
- Note any noise or vibration.
- Repeat steps 1-6 to complete all throttle angles.
- Check for TCC apply in THIRD and FOURTH gear. Typical apply speeds in FOURTH gear range from 72-88 km/h (45-55 mph) depending on engine size, engine type and axle ratio.
- Note the TCC apply point. When the TCC applies there should be a noticeable drop in engine speed and a drop in slip speed to below 100 RPM. If the TCC apply can not be detected:
- Check for DTCs.
- Refer to Torque Converter Diagnosis Procedure .
- Lightly tap and release the brake pedal. The TCC will release.
- Note the TCC apply point. When the TCC applies there should be a noticeable drop in engine speed and a drop in slip speed to below 100 RPM. If the TCC apply can not be detected:
IMPORTANT:
The TCC will not engage until the engine is in closed loop operation. The vehicle must be in a near-cruise condition, not accelerating or coasting, and on a level road surface.