Street Smart - December - 2015

Toyota/Lexus 8-Speed Transmission Is Here!

Toyota and Lexus 8-speed transmissions are on the road and are already showing up in shops.

The first to be introduced was the AA80E, which appeared in the Lexus GS 460 2008-11, Lexus IS F 2008-14, and Lexus LS 460 2007-14.

That was followed by the AA81E, which showed up in the Lexus GS 350 2011-14, Lexus IS350/350C, and Lexus IS250/250C 2014-up.

Use the chart to identify the difference between the gear ratios in the A760H 6-speed, used in AWD models, versus the AA81E 8-speed, used in the 2WD models (figure 1).

The transmission valve body assembly consists of the upper and lower valve bodies and nine shift solenoids. Here are the solenoid locations and functions: (figure 2).

If you need to remove the valve body, remove the 17 bolts shown (figure 3). Once the valve body is on the bench use Figure 4, 5 and 6 for Valve identification and check ball locations.

These transmissions use two planetary gear units to achieve eight speeds.

The rear planetary is a Ravigneaux-type gear unit, which consists of pairs of sun gears (middle and rear) and planetary pinion gears (long and short) with different diameters within a single planetary assembly.

The solenoid operation and clutch application charts (figure 7) show what’s happening to achieve each gear range, and can help you identify where to look for a problem.


Once you’ve determined which clutch or brake is at fault, you can air check that component. (figure 8) Regulate your air pressure to 25-30 PSI so you don’t get a fault reading. Listen for the clutch to engage while applying air to the piston hole.

If the clutches pass the air check, examine the valve body for wear or stuck shift valves. If the shift valves are free and there are no signs of excessive bore wear, you’re probably looking at replacing solenoids.

But if you find excessive leaking during your air check, you’ll probably be going inside. In that case, plan on replacing the molded pistons, even if they feel soft, because they tend to shrink and leak.

This unit has only one sprag; refer to the illustration (figure 9) for proper rotation. Hold the rear planetary gear assembly and turn the one-way clutch.

The one-way clutch should freely counterclockwise and lock when you try to turn it clockwise.

Use the clutch clearance specs (figure 10) to check the clearance for all clutch and brake packs.

It’s a good idea to use genuine Toyota ATF-WS. Additives or aftermarket fluids identified as compatible may result in shift problems or internal damage. ATF-WS isn’t compatible with T-IV or Dexron ATF.

REGISTRATION

After you’ve replaced or repaired the transmission, you’ll need to input the transmission compensation code (figure 11) into the TCM (refer to Procedure 1).

With the transmission installed, the Quick Response (QR) code label will be positioned where you won’t be able to read the code. So always record the transmission compensation code or input it using the Techstream before installing the automatic transmission.

If you’re replacing the TCM, you’ll have to input the existing transmission compensation code into the new TCM (refer to Procedure 2).

PROCEDURE 1
Set Transmission Compensation Code into TCM

Transmission compensation codes are unique, 60-digit alphanumeric values printed on a QR label on the transmission. If you input an incorrect transmission compensation code, it may cause shift shock.

  1. Record the transmission compensation code specified on the QR label.
  2. Move the shift lever to N or P.
  3. Connect the Techstream to the DLC3.
  4. Key on, engine off.
  5. Turn the Techstream on.
  6. Enter the following menus: Powertrain/ECT/Utility/A/T Code Registration.
  7. Select “Set Compensation Code.”
  8. Register the compensation code.
  9. Manually input the transmission compensation code.
  10. Check that the compensation code displayed on the screen is correct by comparing it with the 60-digit alphanumeric value on the QR label.
  11. Set the compensation code into the TCM.

PROCEDURE 2
Transfer Transmission Compensation Code

Transmission compensation codes are unique, 60-digit alphanumeric values printed on a QR label on the transmission. If you input an incorrect transmission compensation code, it may cause shift shock.

You can use this procedure when the TCM you’re replacing can still transmit its registered transmission compensation code to the Techstream.

  1. Read the transmission compensation code.
    1. Move the shift lever to N or P.
    2. Connect the Techstream to the DLC3.
    3. Key on, engine off.
    4. Turn the Techstream on.
    5. Enter the following menus: Powertrain/ECT/Utility/A/T Code Registration.
    6. Select “Read Compensation Code.”
      IMPORTANT: Never use the code printed on the transmission QR label, even if you can’t read the transmission compensation code with the Techstream. The code printed on an in-service transmission may not match its current characteristics. Replace the TCM with a new one and perform a road test to allow the TCM to learn the transmission characteristics.
    7. Key off.
    8. Replace the TCM.
  2. Set the transmission compensation code.
    1. Key on, engine off.
    2. Turn the Techstream on.
    3. Enter the following menus: Powertrain/ECT/Utility/A/T Code Registration.
    4. Select “Set Compensation Code.”
    5. Press “Open.”
    6. Select “Open.”
    7. Set the compensation code to the TCM.
      Once you’ve Set Compensation Code into the TCM, it’s time for the Initialization.
      Perform Reset Memory (AT initialization) when replacing automatic transmission assembly, TCM, valve body assembly, or solenoids.
      This is only possible with the Techstream; you can’t perform a Reset Memory simply by disconnecting and reconnecting the battery.
  3. Reset Memory procedure
    1. Key off.
    2. Connect the Techstream to the DLC3.
    3. Key on, engine off.
    4. Turn the Techstream on.
    5. Enter the following menus: Powertrain/ECT/Utility/Reset Memory.

After performing Reset Memory, be sure to warm up the engine. Then perform a road test to allow the TCM to learn.

Refer to (figure 12) for road test pattern.

Pattern 1: With the shift lever in D, gradually accelerate to 31 MPH or more; then gradually decelerate to about 19 MPH.

Pattern 2: Drive at about 31 MPH in D4 range. Release the accelerator to allow the vehicle to decelerate gradually to about 6 MPH.

Pattern 3: Accelerate above 31 MPH. Gradually decelerate with the shift lever in M and 5th gear selected.

When you reach 31 MPH, downshift to 4th gear.

At about 25 MPH, downshift to 3rd gear.

At about 19 MPH, downshift to 2nd gear.

LEARNING TIPS

Pattern 1: After gradually accelerating for a distance of about 425 feet for about 15 seconds, gradually decelerate for a distance of about 150 ft. for about 5 seconds.

Pattern 3: Accelerate slightly above 31 MPH. Move the shift lever to M and select 5th gear.

Release the accelerator pedal and allow the vehicle to decelerate gradually. When the vehicle decelerates to about 31 MPH, downshift to 4th gear. Continue decelerating and follow the steps listed in procedure 3.

When decelerating, apply the brakes as necessary to adjust vehicle speed.

*1: The speed, time, and distance values are approximate.

*2: After accelerating, you don’t need to decelerate immediately.

*3: There’s no specific time or distance.

Repeat the road test patterns until the shift shock and engine speed overrun (shift flare) reach an acceptable level.

When repeating the acceleration/ deceleration cycle of a road test pattern, bring the vehicle to a complete stop before accelerating again.

Now you know how to learn the TCM, and that’s not just smart, that’s street smart!