GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1996 🢒 Century 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 3T40 🢒 Road Test
    • Perform the road test following the sequence given.
    • The mph (km/h) shift points vary with actual throttle position and driver habits.
    • Compare the results of the test with the shift speed chart information Shift Speed . Use these results with the diagnosis information contained in the Unit Repair Section in order to evaluate the transmission.
    • Perform this test only when traffic and road conditions permit.
    • Observe all traffic safety regulations.

Garage Shift Check
  1. Start the engine.
  2. Depress the brake pedal.

    3. Important: Gear selections should be immediate and not harsh.

  3. Move the gear selector between the following positions:
    4. • Park to Reverse
    • Reverse to Neutral to Drive

Upshift Control and Torque Converter Clutch (TCC) Apply

Important: The torque converter clutch will not engage if the engine coolant has not reached a minimum operating temperature of approximately 54°C (130°F),

With gear selector in Drive (D), perform the following steps:

  1. Accelerate to the chosen throttle position. Use a steady increasing throttle pressure.
  2. As the transmission upshifts, note the shift speed for each of the following gear engagements:
    3. • 2nd gear
    • 3rd gear
  3. Note the speed shift point for TCC apply. This apply should occur between 37-67 km/h (23-42 mph). If you do not notice the apply, refer to the Preminary Torque Converter Clutch Diagnosis information.

Part Throttle Detent Downshift

At vehicle speeds of 40-88 km/h (25-55 mph), quickly depress the accelerator to a half open position. Verify the following results:

    • The TCC releases.
    • The transmission downshifts to 2nd gear immediately.

Full Throttle Detent Downshift

At vehicle speeds of 40-88 km/h (25-55 mph), quickly depress the accelerator to a wide open position. Verify the following results:

    • The TCC releases.
    • The transmission downshifts to 2nd gear immediately.

Manual Downshifts
  1. At vehicle speeds of 40-88 km/h (25-55 mph), release the accelerator pedal while moving the gear selector to Second gear (2). Observe the following results:
    2. • The TCC releases.
    • The transmission downshifts to 2nd gear immediately.
    • The engine slows the vehicle down.
  2. Move the gear selector to Drive (D) and accelerate to 40 km/h (25 mph). Release the accelerator while moving the gear selector to First gear (1). Observe the following results:
    3. • The TCC releases.
    • The transmission immediately downshifts to 1st gear.
    • The engine slows the vehicle down.

Coasting Downshifts
  1. With the gear selector in Drive (D), accelerate to 3rd gear with the TCC applied.
  2. Release the accelerator pedal and lightly apply the brakes. Observe the following results:
    3. • The TCC releases.
    • 3-2 and 2-1 downshifts occur at speeds shown on the Shift Speed Chart. Refer to Shift Speed .

Manual Gear Range Selection

Manual Second (D2)

  1. With the vehicle stopped, move the gear selector to Second (2) and accelerate in order to observe the 1-2 shift.
  2. Accelerate to 40 km/h (25 mph) and observe the following conditions :
    3. • The 2-3 shift does not occur.
    • The TCC does not engage.

Manual First (D1)

With the vehicle stopped, move the gear selector to First (1). Accelerate to 24 km/h (15 mph) and observe the following conditions:

    • No upshifts occur.
    • The TCC does not engage.

Reverse (R)

With the vehicle stopped, move the gear selector to Reverse (R) and slowly accelerate in order to observe reverse gear operation.